Reflective display comprising a frontlight with extraction features and a light redirecting optical element

ABSTRACT

A display includes a reflective spatial light modulator having a reflective surface, a lightguide comprising a core layer, a first cladding layer, and a light emitting region comprising a plurality of light extraction features arranged in a pattern that varies spatially in the light emitting region to frustrate totally internally reflected light propagating within the core layer such that light exits the core layer in the light emitting region into the first cladding layer. A light redirecting optical element is optically coupled to the second side of the first cladding layer, and includes a plurality of light redirecting features directing frustrated totally internally reflected light from the plurality of light extraction features toward the reflective spatial light modulator.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.13/088,167, entitled “Display illumination device with a film-basedlightguide having stacked incident surfaces,” filed on Apr. 15, 2011which claims the benefit of U.S. Provisional Application No. 61/325,266,entitled “Replaceable illuminated signage system for cooler doors,”filed Apr. 16, 2010; U.S. Provisional Application No. 61/325,252,entitled “Manufacturing device for ultra-low profile film lightguide,”filed Apr. 16, 2010; U.S. Provisional Application No. 61/325,269,entitled “Processing method for optical film lightguide and couplingsystem,” filed Apr. 16, 2010; U.S. Provisional Application No.61/325,271, entitled “Method and apparatus for aligning lightguides in acoupling system,” filed Apr. 16, 2010; U.S. Provisional Application No.61/325,272, entitled “Center aligned lighting configuration forultra-thin LED backlight system for LCDs,” filed Apr. 16, 2010; U.S.Provisional Application No. 61/325,275, entitled “Low profile batterypowered lightguide,” filed Apr. 16, 2010; U.S. Provisional ApplicationNo. 61/325,277, entitled “Method and apparatus for enhanced LCDbacklight,” filed Apr. 16, 2010; U.S. Provisional Application No.61/325,280, entitled “Film coupling system with light propagationmodifications,” filed Apr. 16, 2010; U.S. Provisional Application No.61/325,282, entitled “Heatsinking methods for compact film light guidesystems,” filed Apr. 16, 2010; U.S. Provisional Application No.61/325,262, entitled “Lamination method for a multi-layer opticallightguide film,” filed Apr. 16, 2010; U.S. Provisional Application No.61/325,270, entitled “Edge-enhancement for film coupling technology,”filed Apr. 16, 2010; U.S. Provisional Application No. 61/325,265,entitled “Colored surface illumination by mixing dyes and scatteringfeatures into ink,” filed on Apr. 16, 2010; U.S. Provisional ApplicationNo. 61/347,567, entitled “Light emitting device comprising a film-basedlightguide,” filed May 24, 2010; U.S. Provisional Application No.61/363,342, entitled “Film lightguide with light redirecting elements,”filed Jul. 12, 2010; U.S. Provisional Application No. 61/368,560,entitled “Light emitting device with optical redundancy,” filed Jul. 28,2010; U.S. Provisional Application No. 61/377,888, entitled “Lightemitting device comprising a lightguide film,” filed Aug. 27, 2010; U.S.Provisional Application No. 61/381,077, entitled “Light emitting devicewith externally or internally controlled output,” filed Sep. 9, 2010;U.S. Provisional Application No. 61/415,250, entitled “Light emittingdevice comprising a lightguide film and light turning optical element,”filed Nov. 18, 2010; U.S. Provisional Application No. 61/425,328,entitled “Light emitting device comprising a removable and replaceablelightguide,” filed Dec. 21, 2010; U.S. Provisional Application No.61/441,871, entitled “Front illumination device comprising a film-basedlightguide,” filed Feb. 11, 2011; and U.S. Provisional Application No.61/450,711, entitled “Illumination device comprising a film-basedlightguide,” filed on Mar. 9, 2011; this application also claims thebenefit of U.S. Provisional Application No. 61/986,457, entitled“Illumination device including a relative position maintaining element,”filed Apr. 30, 2014, the entire contents of each of which areincorporated herein by reference.

TECHNICAL FIELD

The subject matter disclosed herein generally relates to lightguides,films, and light emitting devices such as, without limitation, lightfixtures, backlights, frontlights, light emitting signs, passivedisplays, and active displays and their components and methods ofmanufacture.

BACKGROUND

Light emitting devices are needed that have a very thin form factor thatcan generate light with specific angular light output profiles.Conventionally, in order to reduce the thickness of displays andbacklights, edge-lit configurations using rigid lightguides have beenused to receive light from the edge of and direct light out of a largerarea surface. These types of light emitting devices are typically housedin relatively thick, rigid frames that do not allow for component ordevice flexibility and require long lead times for design changes. Thevolume of these devices remains large and often includes thick or largeframes or bezels around the device. The thick lightguides (typically 2millimeters (mm) and larger) limit the design configurations, productionmethods, and illumination modes. The ability to further reduce thethickness and overall volume of these area light emitting devices hasbeen limited by the ability to couple sufficient light flux into athinner lightguide.

SUMMARY

In one aspect, a display includes a reflective spatial light modulatorhaving a reflective surface. A lightguide of the display includes a corelayer having opposing surfaces with a thickness not greater than 0.5millimeters therebetween wherein light propagates by total internalreflection between the opposing surfaces; a first cladding layer havinga first side optically coupled to the core layer and an opposing secondside; a lightguide region; an array of coupling lightguides continuouswith the lightguide region, each coupling lightguide of the array ofcoupling lightguides terminating in a bounding edge, and each couplinglightguide folded in a fold region such that the bounding edges of thearray of coupling lightguides are stacked; and a light emitting regioncomprising a plurality of light extraction features arranged in apattern that varies spatially in the light emitting region, theplurality of light extraction features frustrating totally internallyreflected light propagating within the core layer such that light exitsthe core layer in the light emitting region into the first claddinglayer. A light source is positioned to emit light into the stackedbounding edges, the light propagating within the array of couplinglightguides to the lightguide region, with light from each couplinglightguide combining and totally internally reflecting within thelightguide region. A light redirecting optical element is opticallycoupled to the second side of the first cladding layer. The lightredirecting optical element includes a plurality of light redirectingfeatures directing frustrated totally internally reflected light fromthe plurality of light extraction features toward the reflective spatiallight modulator. The plurality of light redirecting features occupy lessthan 50% of a surface of the light redirecting optical element in thelight emitting region. The core layer has an average thickness in thelight emitting region, the light emitting region has a largest dimensionin a plane of the light emitting region orthogonal to a thicknessdirection of the core layer, and the largest dimension of the lightemitting region divided by the average thickness of the core layer inthe light emitting region is greater than 100.

In another aspect, a display includes a reflective spatial lightmodulator having a reflective surface. A first lightguide of the displayincludes a core layer having opposing surfaces with a thickness notgreater than 0.5 millimeters therebetween, a lightguide region and alight emitting region. The first lightguide is defined by the opposingsurfaces guiding light by total internal reflection. A first claddinglayer has a first side optically coupled to the core layer and anopposing second side. An array of coupling lightguides continuous iswith the lightguide region of the first lightguide. Each couplinglightguide of the array of coupling lightguides terminates in a boundingedge, and each coupling lightguide is folded in a fold region such thatthe bounding edges of the array of coupling lightguides are stacked. Aplurality of light extraction features is arranged within the lightemitting region in a pattern that varies spatially in the light emittingregion. The plurality of light extraction features frustrate totallyinternally reflected light propagating between the opposing surfaces ofthe core layer such that light exits the core layer in the lightemitting region into the first cladding layer. A light source ispositioned to emit light into the stacked bounding edges. The lightpropagates within the array of coupling lightguides to the lightguideregion, with light from each coupling lightguide combining and totallyinternally reflecting within the lightguide region. A light redirectingoptical element is optically coupled to the second side of the firstcladding layer. The light redirecting optical element includes aplurality of light redirecting features directing a first portion of thefrustrated totally internally reflected light from the plurality oflight extraction features toward the reflective spatial light modulator.The display also includes a second lightguide including the core layer.The second lightguide is defined by a second portion of the frustratedtotally internally reflected light from the first lightguide propagatingby total internal reflection between a surface of the first lightguideand an area of a surface of the light redirecting optical elementbetween the plurality of light redirecting features.

In yet another aspect, a display includes a reflective spatial lightmodulator having a reflective surface. A first lightguide of the displayincludes a core layer having opposing surfaces with a thickness notgreater than 0.5 millimeters therebetween, a lightguide region and alight emitting region. The first lightguide is defined by the opposingsurfaces guiding light by total internal reflection. An array ofcoupling lightguides is continuous with the lightguide region. Eachcoupling lightguide of the array of coupling lightguides terminates in abounding edge, and each coupling lightguide is folded in a fold regionsuch that the bounding edges of the array of coupling lightguides arestacked. A light source emits light into the stacked bounding edges. Thelight propagates within the array of coupling lightguides to thelightguide region, with light from each coupling lightguide combiningand totally internally reflecting within the lightguide region. A firstcladding layer has a first side optically coupled to the core layer andan opposing second side. A plurality of light extraction features arearranged within the light emitting region in a pattern that variesspatially in the light emitting region. The plurality of lightextraction features frustrate the totally internally reflected lightfrom the array of coupling lightguides propagating in the firstlightguide between the opposing surfaces of the core layer such thatlight exits the core layer in the light emitting region into the firstcladding layer. A light redirecting optical element is optically coupledto the second side of the first cladding layer. The light redirectingoptical element includes a plurality of light redirecting featuresdirecting a first portion of the frustrated totally internally reflectedlight from the plurality of light extraction features back through thefirst cladding layer and the core layer to the reflective spatial lightmodulator. The display includes a second lightguide including the corelayer. The second lightguide is defined by a portion of the frustratedtotally internally reflected light from the first lightguide propagatingby total internal reflection between a surface of the first lightguideand an area of a surface of the light redirecting optical element. Theplurality of light redirecting features occupy less than 50% of thesurface of the light redirecting optical element. The area of thesurface of the light redirecting element is defined between theplurality of light redirecting features and reflects by total internalreflection a second portion of the frustrated totally internallyreflected light from the plurality of light extraction features backthrough the first cladding layer and into the core layer where thesecond portion of the frustrated totally internally reflected lighttotally internally reflects from the surface of the first lightguide andis subsequently reflected by one or more light redirecting features ofthe plurality of light redirecting features toward the reflectivespatial light modulator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of one embodiment of a light emitting deviceincluding a light input coupler disposed on one side of a lightguide.

FIG. 2 is a perspective view of one embodiment of a light input couplerwith coupling lightguides folded in the −y direction.

FIG. 3 is a top view of one embodiment of a light emitting device withtwo light input couplers disposed on the same side of a lightguidewherein the optical axes of the light sources are oriented substantiallytoward each other.

FIG. 4 is a top view of one embodiment of a light emitting deviceincluding three light input couplers.

FIG. 5 is a cross-sectional side view of one embodiment of a lightemitting device including a light input coupler and lightguide with areflective optical element disposed adjacent a surface.

FIG. 6 is a perspective view of one embodiment of a light emittingdevice with a light mixing region wrapped around a relative positionmaintaining element and a stack of coupling lightguides.

FIG. 7 is a top view of one embodiment of a coupling lightguide in threedifferent positions.

FIG. 8 is a top view of one embodiment of a light input couplerincluding a film-based lightguide with staggered coupling lightguides.

FIG. 9 is a top view of one embodiment of a light emitting deviceincluding coupling lightguides with a plurality of first reflectivesurface edges and a plurality of second reflective surface edges withineach coupling lightguide.

FIG. 10 is an enlarged perspective view of the input end of the couplinglightguides of FIG. 9.

FIG. 11 is a top view of one embodiment of a film-based lightguideincluding an array of tapered coupling lightguides.

FIG. 12 is a perspective top view of a light emitting device of oneembodiment including the film-based lightguide of FIG. 11 and a lightsource.

FIG. 13 is top view of one embodiment of a film-based lightguideincluding an array of oriented coupling lightguides with tapered lightcollimating lateral edges adjacent the input surface and light turningedges between the light input surface and the light mixing region of thefilm-based lightguide.

FIG. 14 is a cross-sectional side view of one embodiment of a spatialdisplay including a frontlight.

FIG. 15 is a cross-sectional side view of one embodiment of a lightemitting display including a lightguide that further functions as a topsubstrate for a reflective spatial light modulator.

FIG. 16 is a perspective view of one embodiment of a light emittingdevice including a film-based lightguide that further functions as a topsubstrate for the reflective spatial light modulator with the lightsource disposed on a circuit board physically coupled to the flexibleconnector.

FIG. 17 is a top view of one embodiment of a film-based lightguideincluding an array of coupling lightguides with varying separationdistances between adjacent coupling lightguides.

FIG. 18 is a perspective view of one embodiment of a light input couplerand lightguide including a relative position maintaining elementdisposed proximate a linear fold region.

FIG. 19 is a perspective view of one embodiment of a relative positionmaintaining element (RPME) including a spine and truncated angled teeth.

FIG. 20 is a top view of one embodiment of a film-based lightguideincluding a light mixing region extending past the light emittingregion.

FIG. 21 is a cross-sectional side view of a portion of one embodiment ofa spatial display illuminated by a frontlight including a film-basedlightguide optically coupled to a reflective spatial light modulator anda scratch resistant hardcoating on a hardcoating substrate opticallycoupled to the film-based lightguide,

FIG. 22 is a top view of one embodiment of a light emitting deviceincluding light sources and photodetectors in two light input couplers.

FIG. 23 is a top view of one embodiment of a film-based lightguideincluding an array of coupling lightguides and a sacrificial couplinglightguide including a perforation line.

FIG. 24 is a perspective view of the film-based lightguide of FIG. 23wherein the array of coupling lightguides and the sacrificial couplinglightguide are folded and stacked.

FIG. 25 is a cross-sectional side view of a portion of one embodiment ofa spatial display illuminated by a frontlight including a film-basedlightguide adhered and optically coupled to a color reflective displaysuch that the light from the frontlight is directed toward the colorfilters of the color reflective display.

FIG. 26 is a top view of one embodiment of a light emitting deviceincluding a first light input coupler coupling light into a sub-displaylight emitting region of the film-based lightguide and a second lightinput coupler and third light input coupler coupling light into a maindisplay light emitting region of the film-based lightguide.

FIG. 27 is a top view of one embodiment of a light emitting deviceincluding a main display and a sub-display illuminated by the lightemitting device of FIG. 26.

FIG. 28 is a perspective view of one embodiment of a wrapped lightguideincluding a film based lightguide, an array of coupling lightguidespositioned within a cavity of a light input coupler housing, and aconformal wrap material inserted into the cavity.

FIG. 29 is a cross-sectional side view of a portion of one embodiment ofa light emitting device including the light source, the lightguide, alight input coupler, and a flexible wrap positioned around the folded,stacked array of coupling lightguides; and the wrap includes alignmentguide holes in alignment guide regions and perforations that can be usedto remove the alignment guide regions of the wrap.

FIG. 30 is a perspective view of one embodiment of a relative positionmaintaining element (RPME) including a spine, angled teeth, and groovesin the spine region between the angled teeth such that the RPME can bebent and/or snapped and broken apart along the grooves.

FIGS. 31, 32, and 33 are different perspective views of one embodimentof a relative position maintaining element including a spine and angledteeth that extend from beneath the spine.

FIG. 34 is a cross-sectional side view of one embodiment of a lightemitting device comprising low angle light directing features.

FIG. 35 is a cross-sectional side view of one embodiment of a lightemitting device comprising light turning features.

FIG. 36 is a perspective view of one embodiment of a light emittingdevice comprising a phase compensation element.

FIG. 37 is a cross-sectional side view of one embodiment of a lightemitting device comprising light turning features and low angledirecting features.

DETAILED DESCRIPTION

The features and other details of several embodiments will now be moreparticularly described. It will be understood that particularembodiments described herein are shown by way of illustration and not aslimitations. The principal features can be employed in variousembodiments without departing from the scope of any particularembodiment. All parts and percentages are by weight unless otherwisespecified.

DEFINITIONS

“Electroluminescent display” is defined herein as a means for displayinginformation wherein the legend, message, image or indicia thereon isformed by or made more apparent by an electrically excitable source ofillumination. This includes illuminated cards, transparencies, pictures,printed graphics, fluorescent signs, neon signs, channel letter signs,light box signs, bus-stop signs, illuminated advertising signs, EL(electroluminescent) signs, LED signs, edge-lit signs, advertisingdisplays, liquid crystal displays, electrophoretic displays, point ofpurchase displays, directional signs, illuminated pictures, and otherinformation display signs. Electroluminescent displays can beself-luminous (emissive), back-illuminated (back-lit), front illuminated(front-lit), edge-illuminated (edge-lit), waveguide-illuminated or otherconfigurations wherein light from a light source is directed throughstatic or dynamic means for creating images or indicia.

“Optically coupled” as defined herein refers to coupling of two or moreregions or layers such that the luminance of light passing from oneregion to the other is not substantially reduced by Fresnel interfacialreflection losses due to differences in refractive indices between theregions. “Optical coupling” methods include methods of coupling whereinthe two regions coupled together have similar refractive indices orusing an optical adhesive with a refractive index substantially near orbetween the refractive index of the regions or layers. Examples of“optical coupling” include, without limitation, lamination using anindex-matched optical adhesive, coating a region or layer onto anotherregion or layer, or hot lamination using applied pressure to join two ormore layers or regions that have substantially close refractive indices.Thermal transferring is another method that can be used to opticallycouple two regions of material. Forming, altering, printing, or applyinga material on the surface of another material are other examples ofoptically coupling two materials. “Optically coupled” also includesforming, adding, or removing regions, features, or materials of a firstrefractive index within a volume of a material of a second refractiveindex such that light propagates from the first material to the secondmaterial. For example, a white light scattering ink (such as titaniumdioxide in a methacrylate, vinyl, or polyurethane based binder) may beoptically coupled to a surface of a polycarbonate or silicone film byinkjet printing the ink onto the surface. Similarly, a light scatteringmaterial such as titanium dioxide in a solvent applied to a surface mayallow the light scattering material to penetrate or adhere in closephysical contact with the surface of a polycarbonate or silicone filmsuch that it is optically coupled to the film surface or volume.

“Lightguide” or “waveguide” refers to a region bounded by the conditionthat light rays propagating at an angle that is larger than the criticalangle will reflect and remain within the region. In a lightguide, thelight will reflect or TIR (totally internally reflect) if the angle (α)satisfies the condition α>sin⁻¹(n₂/n₁), where n₁ is the refractive indexof the medium inside the lightguide and n₂ is the refractive index ofthe medium outside the lightguide. Typically, n₂ is air with arefractive index of n≈1; however, high and low refractive indexmaterials can be used to achieve lightguide regions. A lightguide doesnot need to be optically coupled to all of its components to beconsidered as a lightguide. Light may enter from any surface (orinterfacial refractive index boundary) of the waveguide region and maytotally internally reflect from the same or another refractive indexinterfacial boundary. A region can be functional as a waveguide orlightguide for purposes illustrated herein as long as the thickness islarger than the wavelength of light of interest. For example, alightguide may be a 5 micron region or layer of a film or it may be a 3millimeter sheet including a light transmitting polymer.

“In contact” and “disposed on” are used generally to describe that twoitems are adjacent one another such that the whole item can function asdesired. This may mean that additional materials can be present betweenthe adjacent items, as long as the item can function as desired.

A “film” as used herein refers to a thin extended region, membrane, orlayer of material.

A “bend” as used herein refers to a deformation or transformation inshape by the movement of a first region of an element relative to asecond region, for example. Examples of bends include the bending of aclothes rod when heavy clothes are hung on the rod or rolling up a paperdocument to fit it into a cylindrical mailing tube. A “fold” as usedherein is a type of bend and refers to the bend or lay of one region ofan element onto a second region such that the first region covers atleast a portion of the second region. An example of a fold includesbending a letter and forming creases to place it in an envelope. A folddoes not require that all regions of the element overlap. A bend or foldmay be a change in the direction along a first direction along a surfaceof the object. A fold or bend may or may not have creases and the bendor fold may occur in one or more directions or planes such as 90 degreesor 45 degrees. A bend or fold may be lateral, vertical, torsional, or acombination thereof.

Light Emitting Device

In one embodiment, a light emitting device includes a first lightsource, a light input coupler, a light mixing region, and a lightguideincluding a light emitting region with a light extraction feature. Inone embodiment, the first light source has a first light source emittingsurface, the light input coupler includes an input surface disposed toreceive light from the first light source and transmit the light throughthe light input coupler by total internal reflection through a pluralityof coupling lightguides. In this embodiment, light exiting the couplinglightguides is re-combined and mixed in a light mixing region anddirected through total internal reflection within a lightguide orlightguide region. Within the lightguide, a portion of incident light isdirected within the light extracting region by light extracting featuresinto a condition whereupon the angle of light is less than the criticalangle for the lightguide and the directed light exits the lightguidethrough the lightguide light emitting surface.

In a further embodiment, the lightguide is a film with light extractingfeatures below a light emitting device output surface within the film.The film is separated into coupling lightguide strips which are foldedsuch that the coupling lightguide strips form a light input coupler witha first input surface formed by the collection of edges of the couplinglightguide strips.

In one embodiment, the light emitting device has an optical axis definedherein as the direction of peak luminous intensity for light emittingfrom the light emitting surface or region of the device for devices withoutput profiles with one peak. For optical output profiles with morethan one peak and the output is symmetrical about an axis, such as witha “batwing” type profile, the optical axis of the light emitting deviceis the axis of symmetry of the light output. In light emitting deviceswith angular luminous intensity optical output profiles with more thanone peak which are asymmetrical about an axis, the light emitting deviceoptical axis is the angular weighted average of the luminous intensityoutput. For non-planar output surfaces, the light emitting deviceoptical axis is evaluated in two orthogonal output planes and may be aconstant direction in a first output plane and at a varying angle in asecond output plane orthogonal to the first output plane. For example,light emitting from a cylindrical light emitting surface may have a peakangular luminous intensity (thus light emitting device optical axis) ina light output plane that does not include the curved output surfaceprofile and the angle of luminous intensity could be substantiallyconstant about a rotational axis around the cylindrical surface in anoutput plane including the curved surface profile. Thus, in thisexample, the peak angular intensity is a range of angles. When the lightemitting device has a light emitting device optical axis in a range ofangles, the optical axis of the light emitting device includes the rangeof angles or an angle chosen within the range. The optical axis of alens or element is the direction of which there is some degree ofrotational symmetry in at least one plane and as used herein correspondsto the mechanical axis. The optical axis of the region, surface, area,or collection of lenses or elements may differ from the optical axis ofthe lens or element, and as used herein is dependent on the incidentlight angular and spatial profile, such as in the case of off-axisillumination of a lens or element.

Light Input Coupler

In one embodiment, a light input coupler includes a plurality ofcoupling lightguides disposed to receive light emitting from a lightsource and channel the light into a lightguide. In one embodiment, theplurality of coupling lightguides are strips cut from a lightguide filmsuch that each coupling lightguide strip remains un-cut on at least oneedge but can be rotated or positioned (or translated) substantiallyindependently from the lightguide to couple light through at least oneedge or surface of the strip. In another embodiment, the plurality ofcoupling lightguides are not cut from the lightguide film and areseparately optically coupled to the light source and the lightguide. Inanother embodiment, the light emitting device includes a light inputcoupler having a core region of a core material and a cladding region orcladding layer of a cladding material on at least one surface or edge ofthe core material with a refractive index less than a refractive indexof the core material. In other embodiment, the light input couplerincludes a plurality of coupling lightguides wherein a portion of lightfrom a light source incident on a surface of at least one strip isdirected into the lightguide such that light travels in a waveguidecondition. The light input coupler may also include one or more of thefollowing: a strip folding device, a strip holding element, and an inputsurface optical element.

In one embodiment, a first array of light input couplers is positionedto input light into the light mixing region, light emitting region, orlightguide region and a separation distance between the light inputcouplers varies. In one embodiment, a light emitting device includes atleast three light input couplers disposed along a side of a film havinga separation distance between a first pair of input couplers along theside of the film different than a separation distance between a secondpair of input couplers along the side of the film. For example, in oneembodiment a separation distance between the first pair of inputcouplers along the side of the film is great than a separation distancebetween a second pair of input couplers along the side of the film.

Light Source

In one embodiment, a light emitting device includes at least one lightsource selected from a group: fluorescent lamp, cylindrical cold-cathodefluorescent lamp, flat fluorescent lamp, light emitting diode, organiclight emitting diode, field emissive lamp, gas discharge lamp, neonlamp, filament lamp, incandescent lamp, electroluminescent lamp,radiofluorescent lamp, halogen lamp, incandescent lamp, mercury vaporlamp, sodium vapor lamp, high pressure sodium lamp, metal halide lamp,tungsten lamp, carbon arc lamp, electroluminescent lamp, laser, photonicbandgap based light source, quantum dot based light source, highefficiency plasma light source, microplasma lamp. The light emittingdevice may include a plurality of light sources arranged in an array, onopposite sides of lightguide, on orthogonal sides of a lightguide, on 3or more sides of a lightguide, or on 4 sides of a substantially planerlightguide. The array of light sources may be a linear array withdiscrete LED packages includes at least one LED die. In anotherembodiment, a light emitting device includes a plurality of lightsources within one package disposed to emit light toward a light inputsurface. In one embodiment, the light emitting device includes 1, 2, 3,4, 5, 6, 8, 9, 10, or more than 10 light sources. In another embodiment,the light emitting device includes an organic light emitting diodedisposed to emit light as a light emitting film or sheet. In anotherembodiment, the light emitting device includes an organic light emittingdiode disposed to emit light into a lightguide.

In one embodiment, a light emitting device includes at least onebroadband light source that emits light in a wavelength spectrum largerthan 100 nanometers. In another embodiment, a light emitting deviceincludes at least one narrowband light source that emits light in anarrow bandwidth less than 100 nanometers. In another embodiment, alight emitting device includes at least one broadband light source thatemits light in a wavelength spectrum larger than 100 nanometers or atleast one narrowband light source that emits light in a narrow bandwidthless than 100 nanometers. In one embodiment a light emitting deviceincludes at least one narrowband light source with a peak wavelengthwithin a range selected from the group: 300 nm-350 nm, 350 nm-400 nm,400 nm-450 nm, 450 nm-500 nm, 500 nm-550 nm, 550 nm-600 nm, 600 nm-650nm, 650 nm-700 nm, 700 nm-750 nm, 750 nm-800 nm, and 800 nm-1200 nm. Thelight sources may be chosen to match the spectral qualities of red,green and blue such that collectively when used in a light emittingdevice used as a display, the color gamut area is at least one selectedfrom the group: 70% NTSC, 80% NTSC, 90% NTSC, 100% NTSC, and 60%, 70%,80%, 90%, and 95% of the visible CIE u′ v′ color gamut of a standardviewer. In one embodiment, at least one light source is a white LEDpackage including a red, green, and blue LED.

In another embodiment, at least two light sources with different colorsare disposed to couple light into the lightguide through at least onelight input coupler. In another embodiment, a light emitting deviceincludes at least three light input couplers, at least three lightsources with different colors (red, green and blue for example) and atleast three lightguides. In another embodiment, a light source furtherincludes at least one selected from the group: reflective optic,reflector, reflector cup, collimator, primary optic, secondary optic,collimating lens, compound parabolic collimator, lens, reflective regionand input coupling optic. The light source may also include an opticalpath folding optic such as a curved reflector that can enable the lightsource (and possibly heat-sink) to be oriented along a different edge ofthe light emitting device. The light source may also include a photonicbandgap structure, nano-structure or other three-dimensional arrangementthat provides light output with an angular FWHM less than one selectedfrom the group: 120 degrees, 100 degrees, 80 degrees, 60 degrees, 40degrees, and 20 degrees.

In another embodiment, a light emitting device includes a light sourceemitting light in an angular full-width at half maximum intensity ofless than one selected from 150 degrees, 120 degrees, 100 degrees, 80degrees, 70 degrees, 60 degrees, 50 degrees, 40 degrees, 30 degrees, 20degrees, and 10 degrees. In another embodiment, the light source furtherincludes at least one selected from the group: a primary optic,secondary optic, and photonic bandgap region and the angular full-widthat half maximum intensity of the light source is less than one selectedfrom 150 degrees, 120 degrees, 100 degrees, 80 degrees, 70 degrees, 60degrees, 50 degrees, 40 degrees, 30 degrees, 20 degrees, and 10 degrees.

LED Array

In one embodiment, the light emitting device includes a plurality ofLEDs or LED packages wherein the plurality of LEDs or LED packagesincludes an array of LEDs. The array components (LEDs or electricalcomponents) may be physically (and/or electrically) coupled to a singlecircuit board or they may be coupled to a plurality of circuit boardsthat may or may not be directly physically coupled (i.e. such as not onthe same circuit board). In one embodiment, the array of LEDs is anarray including at least two selected from the group: red, green, blue,and white LEDs. In this embodiment, the variation in the white point dueto manufacturing or component variations can be reduced. In anotherembodiment, the LED array includes at least one cool white LED and onered LED. In this embodiment, the CRI, or Color Rendering Index, ishigher than the cool white LED illumination alone. In one embodiment,the CRI of at least one selected from the group: a light emittingregion, the light emitting surface, light fixture, light emittingdevice, display driven in a white mode including the light emittingdevice, and sign is greater than one selected from the group: 70, 75,80, 85, 90, 95, and 99. In another embodiment, the NIST Color QualityScale (CQS) of at least one selected from the group: a light emittingregion, the light emitting surface, light fixture, light emittingdevice, display driven in a white mode including the light emittingdevice, or sign is greater than one selected from the group: 70, 75, 80,85, 90, 95, and 99. In another embodiment, a display including the lightemitting device has a color gamut greater than 70%, 80%, 85%, 90%, 95%,100%, 105%, 110%, 120%, and 130% that of the NTSC standard. In anotherembodiment, the LED array includes white, green, and red LEDs. Inanother embodiment, the LED array includes at least one green and blueLED and two types of red LEDs with one type having a lower luminousefficacy or a lower wavelength than the other type of red LED. As usedherein, the white LED may be a phosphor converted blue LED or a phosphorconverted UV LED.

In another embodiment, the input array of LEDs can be arranged tocompensate for uneven absorption of light through longer verses shorterlightguides. In another embodiment, the absorption is compensated for bydirecting more light into the light input coupler corresponding to thelonger coupling lightguides or longer lightguides. In anotherembodiment, light within a first wavelength band is absorbed within thelightguide more than light within a second wavelength band and a firstratio of the radiant light flux coupled into the light input couplerwithin the first wavelength band divided by the radiant light fluxcoupled into the light input coupler within the second wavelength bandis greater than a second ratio of the radiant light flux emitted fromthe light emitting region within the first wavelength band divided bythe radiant light flux emitted from the light emitting region within thesecond wavelength band.

Laser

In one embodiment, the light emitting device includes one or more lasersdisposed to couple light into one or more light input couplers or thesurface of one or more coupling lightguides. In one embodiment, thedivergence of one or more light sources is less than one selected fromthe group: 20 milliradians, 10 milliradians, 5 milliradians, 3milliradians, and 2 milliradians. In another embodiment, the lightmixing region includes a light scattering or light reflecting regionthat increases the angular FWHM of the light from one or more laserswithin the light mixing region before entering into the light emittingregion of the lightguide or light emitting surface region of the lightemitting device. In a further embodiment, the light scattering regionwithin the light mixing region is a volumetric or surface lightscattering region with an angular FWHM of transmitted light less thanone selected from the group: 50 degrees, 40 degrees, 30 degrees, 20degrees, 10 degrees, 5 degrees, and 2 degrees when measured normal tothe large area surface of the film in the region with a 532 nm laserdiode with a divergence less than 5 milliradians. In a furtherembodiment, the haze of the diffuser in the light mixing region is lessthan one selected from the group: 50%, 40%, 30%, 20%, 10%, 5%, and 2%when measured normal to the large area surface of the film (such asparallel to the light emitting surface).

Color Tuning

In one embodiment, the light emitting device includes two or more lightsources and the relative output of the two light sources is adjusted toachieve a desired color in a light emitting region of the lightguide oran area of light output on the light emitting device including aplurality of lightguides overlapping in the region. For example, in oneembodiment, the light emitting device includes a red, green, and blueLED disposed to couple light into the light input surface of a stack ofcoupling lightguides. The light mixes within the lightguide and isoutput in a light emitting region of the lightguide. By turning on thered and blue LEDs, for example, one can achieve a purple colored lightemitting region. In another embodiment, the relative light output of thelight sources is adjusted to compensate for the non-uniform spectralabsorption in an optical element of the light emitting device. Forexample, in one embodiment, the output of the blue LED in milliwatts isincreased to a level more than the red output in milliwatts in order tocompensate for more blue light absorption in a lightguide (or blue lightscattering) such that the light emitting region has a substantiallywhite light output in a particular region.

LED Array Location

In one embodiment, a plurality of LED arrays are disposed to couplelight into a single light input coupler or more than one light inputcoupler. In a further embodiment, a plurality of LEDs disposed on acircuit board are disposed to couple light into a plurality of lightinput couplers that direct light toward a plurality of sides of a lightemitting device including a light emitting region. In a furtherembodiment, a light emitting device includes an LED array and lightinput coupler folded behind the light emitting region of the lightemitting device such that the LED array and light input coupler are notvisible when viewing the center of the light emitting region at an angleperpendicular to the surface. In another embodiment, a light emittingdevice includes a single LED array disposed to couple light into atleast one light input coupler disposed to direct light into the lightemitting region from the bottom region of a light emitting device. Inone embodiment, a light emitting device includes a first LED array and asecond LED array disposed to couple light into a first light inputcoupler and a second light input coupler, respectively, wherein thefirst light input coupler and second light input coupler are disposed todirect light into the light emitting region from the top region andbottom region, respectively, of a light emitting device. In a furtherembodiment, a light emitting device includes a first LED array, a secondLED array, and a third LED array, disposed to couple light into a firstlight input coupler, a second light input coupler, and a third lightinput coupler, respectively, disposed to direct light into the lightemitting region from the bottom region, left region, and right region,respectively, of a light emitting device. In another embodiment, a lightemitting device includes a first LED array, a second LED array, a thirdLED array, and a fourth LED array, disposed to couple light into a firstlight input coupler, a second light input coupler, a third light inputcoupler, and a fourth light input coupler, respectively, disposed todirect light into the light emitting region from the bottom region, leftregion, right region, and top region, respectively, of a light emittingdevice.

Wavelength Conversion Material

In another embodiment, the LED is a blue or ultraviolet LED combinedwith a phosphor. In another embodiment, a light emitting device includesa light source with a first activating energy and a wavelengthconversion material which converts a first portion of the firstactivating energy into a second wavelength different than the first. Inanother embodiment, the light emitting device includes at least onewavelength conversion material selected from the group: a fluorophore,phosphor, a fluorescent dye, an inorganic phosphor, photonic bandgapmaterial, a quantum dot material, a fluorescent protein, a fusionprotein, a fluorophores attached to protein to specific functionalgroups (such as amino groups (active ester, carboxylate, isothiocyanate,hydrazine), carboxyl groups (carbodiimide), thiol (maleimide, acetylbromide), azide (via click chemistry or non-specifically(glutaraldehyde))), quantum dot fluorophores, small moleculefluorophores, aromatic fluorophores, conjugated fluorophores, afluorescent dye, and other wavelength conversion material.

In one embodiment, the light source includes a semiconductor lightemitter such as an LED and a wavelength conversion material thatconverts a portion of the light from the emitter to a shorter or longerwavelength. In another embodiment, at least one selected from the group:light input coupler, cladding region, coupling lightguide, input surfaceoptic, coupling optic, light mixing region, lightguide, light extractionfeature or region, and light emitting surface includes a wavelengthconversion material.

Light Input Coupler Input Surface

In one embodiment, the light input coupler includes a collection ofcoupling lightguides with a plurality of edges forming a light couplerinput surface. In another embodiment, an optical element is disposedbetween the light source and at least one coupling lightguide whereinthe optical element receives light from the light source through a lightcoupler input surface. In some embodiments, the input surface issubstantially polished, flat, or optically smooth such that light doesnot scatter forwards or backwards from pits, protrusions or other roughsurface features. In some embodiments, an optical element is disposed tobetween the light source and at least one coupling lightguide to providelight redirection as an input surface (when optically coupled to atleast one coupling lightguide) or as an optical element separate oroptically coupled to at least one coupling lightguide such that morelight is redirected into the lightguide at angles greater than thecritical angle within the lightguide than would be the case without theoptical element or with a flat input surface. The coupling lightguidesmay be grouped together such that the edges opposite the lightguideregion are brought together to form an input surface including theirthin edges.

Stacked Strips or Segments of Film Forming a Light Input Coupler

In one embodiment, the light input coupler is region of a film thatincludes the lightguide and the light input coupler which includes stripsections of the film which form coupling lightguides that are groupedtogether to form a light coupler input surface. The coupling lightguidesmay be grouped together such the edges opposite the lightguide regionare brought together to form an input surface including their thinedges. A planar input surface for a light input coupler can providebeneficial refraction to redirect a portion of the input light from thesurface into angles such that it propagates at angles greater than thecritical angle for the lightguide. In another embodiment, asubstantially planar light transmitting element is optically coupled tothe grouped edges of coupling lightguides. One or more of the edges ofthe coupling lightguides may be polished, melted, smoothed using acaustic or solvent material, adhered with an optical adhesive, solventwelded, or otherwise optically coupled along a region of the edgesurface such that the surface is substantially polished, smooth, flat,or substantially planarized.

In one embodiment, the lateral edges of at least one selected from thegroup: light turning lateral edges of the coupling lightguides, lightcollimating lateral edges of the coupling lightguides, lateral edges ofthe coupling lightguides, lateral edges of the lightguide region,lateral edges of the light mixing region, and lateral edges of the lightemitting region includes an optical smoothing material disposed at aregion of the edge that reduces the surface roughness of the region ofthe edge in at least one of the lateral direction and thicknessdirection. In one embodiment, the optical smoothing material fills ingaps, grooves, scratches, pits, digs, flattens regions aroundprotrusions or other optical blemishes such that more light totallyinternally reflects from the surface from within the core region of thecoupling lightguide.

The light input surface may include a surface of the optical element,the surface of an adhesive, the surface of more than one opticalelement, the surface of the edge of one or more coupling lightguides, ora combination of one or more of the aforementioned surfaces. The lightinput coupler may also include an optical element that has an opening orwindow wherein a portion of light from a light source may directly passinto the coupling lightguides without passing through the opticalelement. The light input coupler or an element or region therein mayalso include a cladding material or region.

Light Redirecting Optical Element

In one embodiment, a light redirecting optical element is disposed toreceive light from at least one light source and redirect the light intoa plurality of coupling lightguides. In another embodiment, the lightredirecting optical element is at least one selected from the group:secondary optic, mirrored element or surface, reflective film such asaluminized PET, giant birefringent optical films such as Vikuiti™Enhanced Specular Reflector Film by 3M Inc., curved mirror, totallyinternally reflecting element, beamsplitter, and dichroic reflectingmirror or film.

Light Collimating Optical Element

In one embodiment, the light input coupler includes a light collimatingoptical element. A light collimating optical element receives light fromthe light source with a first angular full-width at half maximumintensity within at least one input plane and redirects a portion of theincident light from the light source such that the angular full-width athalf maximum intensity of the light is reduced in the first input plane.In one embodiment, the light collimating optical element is one or moreof the following: a light source primary optic, a light source secondaryoptic, a light input surface, and an optical element disposed betweenthe light source and at least one coupling lightguide. In anotherembodiment, the light collimating element is one or more of thefollowing: an injection molded optical lens, a thermoformed opticallens, and a cross-linked lens made from a mold. In another embodiment,the light collimating element reduces the angular full-width at halfmaximum (FWHM) intensity within the input plane and a plane orthogonalto the input plane.

In one embodiment, a light emitting device includes a light inputcoupler and a film-based lightguide. In one embodiment the light inputcoupler includes a light source and a light collimating optical elementdisposed to receive light from one or more light sources and providelight output in a first output plane, second output plane orthogonal tothe first plane, or in both output planes with an angular full-width athalf maximum intensity in air less than one selected from the group: 60degrees, 40 degrees, 30 degrees, 20 degrees, and 10 degrees from theoptical axis of the light exiting the light collimating optical element.

In one embodiment, the collimation or reduction in angular FWHMintensity of the light from the light collimating element issubstantially symmetric about the optical axis. In one embodiment, thelight collimating optical element receives light from a light sourcewith a substantially symmetric angular FWHM intensity about the opticalaxis greater than one selected from the group: 50, 60, 70, 80, 90, 100,110, 120, and 130 degrees and provides output light with an angular FWHMintensity less than one selected from the group: 60, 50, 40, 30, and 20degrees from the optical axis. For example, in one embodiment, the lightcollimating optical element receives light from a white LED with anangular FWHM intensity of about 120 degrees symmetric about its opticalaxis and provides output light with an angular FWHM intensity of about30 degrees from the optical axis.

The angular full-width at half maximum intensity of the lightpropagating within the lightguide can be determined by measuring the farfield angular intensity output of the lightguide from an optical qualityend cut normal to the film surface and calculating and adjusting forrefraction at the air-lightguide interface. In another embodiment, theaverage angular full-width at half maximum intensity of the extractedlight from one or more light extraction features or light extractionregions including light extraction features of the film-based lightguideis less than one selected from the group: 50 degrees, 40 degrees, 30degrees, 20 degrees, 10 degrees, and 5 degrees. In another embodiment,the peak angular intensity of the light extracted from the lightextraction feature is within 50 degrees of the surface normal of thelightguide within the region. In another embodiment, the far-field totalangular full-width at half maximum intensity of the extracted light fromthe light emitting region of the film-based lightguide is less than oneselected from the group: 50 degrees, 40 degrees, 30 degrees, 20 degrees,10 degrees, and 5 degrees and the peak angular intensity is within 50degrees of the surface normal of the lightguide in the light emittingregion.

Coupling Lightguides

In one embodiment, the coupling lightguide is a region wherein lightwithin the region can travel in a waveguide condition and a portion ofthe light input into a surface or region of the coupling lightguidespasses through the coupling lightguide toward a lightguide or lightmixing region. The coupling lightguide, in some embodiments, may serveto geometrically transform a portion of the flux from a light sourcefrom a first shaped area to a second shaped area different from thefirst shaped area. In an example of this embodiment, the light inputsurface of the light input coupler formed from the edges of foldedstrips (coupling lightguides) of a planar film has dimensions of arectangle that is 3 millimeters by 2.7 millimeters and the light inputcoupler couples light into a planar section of a film in the lightmixing region with a cross-sectional dimensions of 40.5 millimeters by0.2 millimeters. In one embodiment, the extended direction of one ormore coupling lightguides is the direction in which the one or morecoupling lightguides extend from a common base area.

Coupling Lightguide Folds and Bends

In one embodiment, a light emitting device includes a light mixingregion disposed between a lightguide and strips or segments cut to formcoupling lightguides, whereby a collection of edges of the strips orsegments are brought together to form a light input surface of the lightinput coupler disposed to receive light from a light source. In oneembodiment, the light input coupler includes a coupling lightguidewherein the coupling lightguide includes at least one fold or bend in aplane such that at least one edge overlaps another edge. In anotherembodiment, the coupling lightguide includes a plurality of folds orbends wherein edges of the coupling lightguide can be abutted togetherin region such that the region forms a light input surface of the lightinput coupler of the light emitting device. In one embodiment, at leastone coupling lightguide includes a strip or a segment that is bent orfolded to radius of curvature of less than 75 times a thickness of thestrip or the segment. In another embodiment, at least one couplinglightguide includes a strip or a segment that is bended or folded toradius of curvature greater than 10 times a thickness of the strip orthe segment. In another embodiment, at least one coupling lightguide isbent or folded such that a longest dimension in a cross-section throughthe light emitting device or coupling lightguide in at least one planeis less than without the fold or bend. Segments or strips may be bent orfolded in more than one direction or region and the directions offolding or bending may be different between strips or segments.

Coupling Lightguide Lateral Edges

In one embodiment, the lateral edges, defined herein as the edges of thecoupling lightguide which do not substantially receive light directlyfrom the light source and are not part of the edges of the lightguideregion. The lateral edges of the coupling lightguide receive lightsubstantially only from light propagating within the coupling lightguide. In one embodiment, the lateral edges are at least one selectedfrom the group: uncoated, coated with a reflecting material, disposedadjacent to a reflecting material, and cut with a specificcross-sectional profile. The lateral edges may be coated, bonded to ordisposed adjacent to a specularly reflecting material, partiallydiffusely reflecting material, or diffuse reflecting material. In oneembodiment, the edges are coated with a specularly reflecting inkincluding nano-sized or micron-sized particles or flakes whichsubstantially reflect the light in a specular manner when the couplinglightguides are brought together from folding or bending. In anotherembodiment, a light reflecting element (such as a multi-layer mirrorpolymer film with high reflectivity) is disposed near the lateral edgeof at least one region of a coupling lightguide disposed, themulti-layer mirror polymer film with high reflectivity is disposed toreceive light from the edge and reflect it and direct it back into thelightguide. In another embodiment, the lateral edges are rounded and thepercentage of incident light diffracted out of the lightguide from theedge is reduced. One method of achieving rounded edges is by using alaser to cut the strips, segments or coupling lightguide region from afilm and edge rounding through control of the processing parameters(speed of cut, frequency of cut, laser power, etc.). Other methods forcreating rounded edges include mechanical sanding/polishing or fromchemical/vapor polishing. In another embodiment, the lateral edges of aregion of a coupling lightguide are tapered, angled, serrated, orotherwise cut or formed such that light from a light source propagatingwithin the coupling lightguide reflects from the edge such that it isdirected into an angle closer to the optical axis of the light source,toward a folded or bent region, or toward a lightguide or lightguideregion.

Width of Coupling Lightguides

In one embodiment, the dimensions of the coupling lightguides aresubstantially equal in width and thickness to each other such that theinput surface areas for each edge surface are substantially the same. Inanother embodiment, the average width of the coupling lightguides, w, isdetermined by the equation: w=MF*W_(LES)/NC, where W_(LES) is the totalwidth of the light emitting surface in the direction parallel to thelight entrance edge of the lightguide region or lightguide receivinglight from the coupling lightguide, NC is the total number of couplinglightguides in the direction parallel to the light entrance edge of thelightguide region or lightguide receiving light from the couplinglightguide, and MF is the magnification factor. In one embodiment, themagnification factor is one selected from the group: 0.7, 0.8, 0.9, 1,1.1, 1.2, 1.3, 1.4, 0.7-1.3, 0.8-1.2, and 0.9-1.1. In anotherembodiment, at least one selected from the group: coupling lightguidewidth, the largest width of a coupling waveguide, the average width ofthe coupling lightguides, and the width of each coupling lightguides isselected from a group of: 0.5 mm-1 mm, 1 mm-2 mm, 2 mm-3 mm, 3 mm-4 mm,5 mm-6 mm, 0.5 mm-2 mm, 0.5 mm-25 mm, 0.5 mm-10 mm, 10-37 mm, and 0.5mm-5 mm. In one embodiment, at least one selected from the group: thecoupling lightguide width, the largest width of a coupling waveguide,the average width of the coupling lightguides, and the width of eachcoupling lightguides is less than 20 millimeters.

In one embodiment, the ratio of the average width of the couplinglightguides disposed to receive light from a first light source to theaverage thickness of the coupling lightguides is greater than oneselected from the group: 1, 2, 4, 5, 10, 15, 20, 40, 60, 100, 150, and200. In another embodiment, a low contact area film is placed betweenthe lateral edges of the coupling lightguide and the folded section. Inanother embodiment, the folded section includes low contact area surfacefeatures such that it provides protection without significantly couplinglight from the lateral and/or surface areas of the coupling lightguides.In another embodiment, a coupling lightguide includes an adhesivedisposed between two regions of the coupling lightguide such that it isadhered to itself and wrapping around a stack of coupling lightguides.

Separation or Gap Between the Coupling Lightguides

In one embodiment, two or more coupling lightguides include a gapbetween the lightguides in the region where they connect to thelightguide region, lightguide region, or light mixing region. In anotherembodiment, the lightguides are formed from a manufacturing methodwherein gaps between the lightguides are generated. For example, in oneembodiment, the lightguides are formed by die cutting a film and thecoupling lightguides have a gap between each other. In one embodiment,the gap between the coupling lightguides is greater than one selectedfrom the group: 0.15, 0.25, 0.5, 1, 2, 4, 5, 10, 25, and 50 millimeters.If the gap between the coupling lightguides is very large relative tothe coupling lightguide width, then the uniformity of the light emittingregion may be reduced (with respect to luminance or color uniformity) insome embodiments if the light mixing region is not sufficiently long ina direction parallel to the optical axis of the light propagating in thelightguide because a side of the lightguide has regions (the gapregions) where light is not entering the lightguide region from couplinglightguides. In one embodiment, a film-based lightguide includes twocoupling lightguides wherein the average of the width of the twocoupling lightguides divided by the width of the gap between the twocoupling lightguides at the region where the two coupling lightguidesjoin the light mixing region or lightguide region is greater than oneselected from the group: 0.1, 0.5, 1, 1.5, 2, 4, 6, 10, 20, 40, and 50.In another embodiment, the film-based lightguide has large gaps betweenthe coupling lightguides and a sufficiently long light mixing region toprovide the desired level of uniformity. In another embodiment, afilm-based lightguide includes two coupling lightguides wherein thewidth of the gap between the two coupling lightguides divided by theaverage of the width of the two coupling lightguides at the region wherethe coupling lightguides join the light mixing region or lightguideregion is greater than one selected from the group: 1, 1.5, 2, 4, 6, 10,20, 40, and 50.

Variable Separation Between Coupling Lightguides

In one embodiment, a first array of coupling lightguides extends fromthe lightguide region or body of a film-based lightguide and theseparation distance between the coupling lightguides at the lightguideregion varies. In another embodiment, the separation distance betweentwo or more coupling lightguides along a first side of a lightguideregion of a film-based lightguide is greater than the separationdistance between two or more coupling lightguides along the side of thelightguide region. In another embodiment, a first pair of couplinglightguides positioned along a side of the lightguide region of thefilm-based lightguide has a first average length and a first separationdistance, and a second pair of coupling lightguides disposed along theside of the lightguide region of the film-based lightguide has a secondaverage length and a second separation distance. In one embodiment, thefirst average length is less than the second average length and thefirst separation distance is larger than the second separation distance.In another embodiment, the first average length is greater than thesecond average length and the first separation distance is larger thanthe second separation distance. In another embodiment, the separationdistance between the coupling lightguides along one side of a lightguideregion of a film-based lightguide decreases and the length of thecoupling lightguides increases. In another embodiment, the separationdistance, taper, and/or average width of two pairs of couplinglightguides vary along a side of a lightguide region from which the twopairs of coupling lightguides extend.

Separation Between the Lightguide Region Edge and the CouplingLightguide Nearest the Edge

In one embodiment, a coupling lightguide nearest the edge of thefilm-based lightguide is spaced from the edge of the film adjacent theside. For example, in one embodiment, the first coupling lightguidealong a side of a film-based lightguide is separated from the edge ofthe lightguide region by a distance greater than 1 mm). In anotherembodiment, the first coupling lightguide along a side of a film-basedlightguide is separated from the edge of the lightguide region by adistance greater than one selected from the group: 0.5, 1, 2, 4, 6, 8,10, 20, and 50 millimeters. In one embodiment, the distance between thelightguide region edge and the first coupling lightguide along a sideimproves the uniformity in the lightguide region due to the light fromthe first coupling lightguide reflecting from the lateral edge of thelightguide region.

Shaped or Tapered Coupling Lightguides

The width of the coupling lightguides may vary in a predeterminedpattern. In one embodiment, the width of the coupling lightguides variesfrom a large width in a central coupling lightguide to smaller width inlightguides further from the central coupling lightguide as viewed whenthe light input edges of the coupling lightguides are disposed togetherto form a light input surface on the light input coupler. In thisembodiment, a light source with a substantially circular light outputaperture can couple into the coupling lightguides such that the light athigher angles from the optical axis are coupled into a smaller widthstrip such that the uniformity of the light emitting surface along theedge of the lightguide or lightguide region and parallel to the inputedge of the lightguide region disposed to receive the light from thecoupling lightguides is greater than one selected from the group: 60%,70%, 80%, 90% and 95%.

Other shapes of stacked coupling lightguides can be envisioned, such astriangular, square, rectangular, oval, etc. that provide matched inputareas to the light emitting surface of the light source. The widths ofthe coupling lightguides may also be tapered such that they redirect aportion of light received from the light source. The lightguides may betapered near the light source, in the area along the coupling lightguidebetween the light source and the lightguide region, near the lightguideregion, or some combination thereof.

The shape of a coupling lightguide is referenced herein from thelightguide region or light emitting region or body of the lightguide.One or more coupling lightguides extending from a side or region of thelightguide region may expand (widen or increase in width) or taper(narrow or decrease in width) in the direction toward the light source.In one embodiment, coupling lightguides taper in one or more regions toprovide redirection or partial collimation of the light traveling withinthe coupling lightguides from the light source toward the lightguideregion. In one embodiment, one or more coupling lightguides widens alongone lateral edge and tapers along the opposite lateral edge. In thisembodiment, the net effect may be that the width remains constant. Thewidening or tapering may have different profiles or shapes along eachlateral side for one or more coupling lightguides. The widening,tapering, and the profile for each lateral edge of each couplinglightguide may be different and may be different in different regions ofthe coupling lightguide. For example, one coupling lightguide in anarray of coupling lightguides may have a parabolic tapering profile onboth sides of the coupling lightguides in the region near the lightsource to provide partial collimation, and at the region starting atabout 50% of the length of the coupling lightguides one lateral edgetapers in a linear angle and the opposite side includes a parabolicshaped edge. The tapering, widening, shape of the profile, location ofthe profile, and number of profiles along each lateral edge may be usedto provide control over one or more selected from the group: spatial orangular color uniformity of the light exiting the coupling lightguidesinto the light mixing region (or light emitting region), spatial orangular luminance uniformity of the light exiting the couplinglightguides into the light mixing region (or light emitting region),angular redirection of light into the light mixing region (or lightemitting region) of the lightguide (which can affect the angular lightoutput profile of the light exiting the light emitting region along withthe shape, size, and type of light extraction features), relative fluxdistribution within the light emitting region, and other lightredirecting benefits such as, without limitation, redirecting more lighttoward a second, extending light emitting region.

Interior Light Directing Edge

In one embodiment, the interior region of one or more couplinglightguides includes an interior light directing edge. The interiorlight directing edge may be formed by cutting or otherwise removing aninterior region of the coupling lightguide. In one embodiment, theinterior light directed edge redirects a first portion of light withinthe coupling lightguide. In one embodiment, the interior light directingedges provide an additional level of control for directing the lightwithin the coupling lightguides and can provide light fluxredistribution within the coupling lightguide and within the lightguideregion to achieve a predetermined light output pattern (such as higheruniformity or higher flux output) in a specific region.

In one embodiment, at least one interior light directing edge ispositioned within a coupling lightguide to receive light propagatingwithin the coupling lightguide within a first angular range from theoptical axis of light traveling within the coupling lightguide anddirect the light to a second, different angular range propagating withinthe coupling lightguide. In one embodiment, the first angular range isselected from the group: 70-89, 70-80, 60-80, 50-80, 40-80, 30-80,20-80, 30-70, and 30-60 degrees; and the second angular range isselected from the group: 0-10, 0-20, 0-30, 0-40, 0-50, 10-40, and 20-60degrees. In one embodiment, a plurality of interior light directingedges are formed after the coupling lightguides are stacked. In anotherembodiment, one or more coupling lightguides have interior lightdirecting edges that form a channel that spatially separates lighttraveling within the coupling lightguide. In one embodiment, a lengthalong the optical axis of light travelling within the couplinglightguide of one or more interior light directing edges is greater thanone selected from the group: 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%of a length from an input surface of the coupling lightguide to thelightguide region or the light mixing region along the optical axis oflight traveling within the coupling lightguide. In another embodiment,one or more coupling lightguides have interior light directing edgespositioned within one selected from the group: 1, 5, 7, 10, 15, 20, 25millimeters from the lightguide region of the film-based lightguide. Inone embodiment, one or more coupling lightguides have interior lightdirecting edges positioned within one selected from the group: 1, 5, 7,10, 15, 20, 25 millimeters from the light input surface of the one ormore coupling lightguides. In a further embodiment, one or more couplinglightguides have at least one interior light directing edge with a widthof the interior light directing edge in a direction parallel to the foldline greater than one selected from the group of: 5, 10, 15, 20, 25, 30,35, 40, 45, 50, and 60 percent of a width of the coupling lightguide atthe lightguide region. In a further embodiment, at least one couplinglightguide has two adjacent interior light directing edges wherein theaverage separation between the interior light directing edges in adirection parallel to a fold line is greater than one selected from thegroup of: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, and 60 percent of thewidth of the coupling lightguide at the lightguide region.

In another embodiment, at least one coupling lightguide includes aplurality of channels defined by at least one interior light directingedge and a lateral edge of the coupling lightguide. In a furtherembodiment, the coupling lightguide includes a channel defined by afirst interior light directing edge and a second interior lightdirecting edge. In one embodiment, one or more channels defined byinterior light directing edges and/or lateral edges of the couplinglightguide separate angular ranges of light from the light source intospatially separated channels that can transfer the spatial separation tothe lightguide region. In one embodiment, the channels are parallel tothe extended direction of an array of coupling lightguides. In anotherembodiment, the light source includes a plurality of light emittingdiodes formed in an array such that the optical axis of a first lightsource enters a first channel defined in a coupling lightguide and theoptical axis of a second source enters a second channel defined in acoupling lightguide. In one embodiment, one or more interior lightdirecting edges extend from within one or more coupling lightguides intothe lightguide region of the lightguide. In another embodiment, thelightguide region has one or more interior light directing edges. In afurther embodiment, the lightguide region has one or more interior lightdirecting edges and one or more coupling lightguides include one or moreinterior light directing edges. In another embodiment, one or moreinterior light directing edges extend from within one or more couplinglightguides into the light emitting region of the lightguide. In thisembodiment, for example, a light source including red, green, and bluelight emitting diodes in a linear array adjacent a first, second, andthird channel of a plurality of coupling lightguides, respectively canbe directed to an alternating first, second, and third pixel regionwithin the light emitting region to create a spatial arrangement ofrepeating red, green, blue, red, green, blue, red, green, blue colorpixels in a light emitting region for a color display or sign. Inanother embodiment, the interior region of the light mixing region orlightguide region includes at least one interior light directing edge.

Coupling Lightguide Orientation Angle

In a further embodiment, at least one portion of the array of couplinglightguides is disposed at a first coupling lightguide orientation angleto the edge of at least one of the light mixing region and lightemitting region which it directs light into. The coupling lightguideorientation angle is defined as the angle between the couplinglightguide axis and the direction parallel to the major component of thedirection of the coupling lightguides to the light emitting region ofthe lightguide. The major component of the direction of the couplinglightguide to the light emitting region of the lightguide is orthogonalto the array direction of the array of coupling lightguides at the lightmixing region (or lightguide region if they extend directly from thelight emitting region). In one embodiment, the orientation angle of acoupling lightguide or the average orientation angle of a plurality ofcoupling lightguides is at least one selected from the group: 1-10degrees, 10-20 degrees, 20-30 degrees, 30-40 degrees, 40-50 degrees,60-70 degrees, 70-80 degrees, 1-80 degrees, 10-70 degrees, 20-60degrees, 30-50 degrees, greater than 5 degrees, greater than 10 degrees,and greater than 20 degrees.

Non-Folded Coupling Lightguide

In a further embodiment, the film-based lightguide includes a non-foldedcoupling lightguide disposed to receive light from the light inputsurface and direct light toward the lightguide region without turningthe light. In one embodiment, the non-folded lightguide is used inconjunction with one or more light turning optical elements, lightcoupling optical elements, coupling lightguides with light turningedges, or coupling lightguides with collimating edges. For example, alight turning optical element may be disposed above or below anon-folded coupling lightguide such that a first portion of light from alight source substantially maintains the direction of its optical axiswhile passing through the non-folded coupling lightguide and the lightfrom the source received by the light turning optical element is turnedto enter into a stacked array of coupling lightguides. In anotherembodiment, the stacked array of coupling lightguides includes foldedcoupling lightguides and a non-folded coupling lightguide.

In another embodiment, the non-folded coupling lightguide is disposednear an edge of the lightguide. In one embodiment, the non-foldedcoupling lightguide is disposed in the middle region of the edge of thelightguide region. In a further embodiment, the non-folded couplinglightguide is disposed along a side of the lightguide region at a regionbetween the lateral sides of the lightguide region. In one embodiment,the non-folded coupling lightguide is disposed at various regions alongone edge of a lightguide region wherein a plurality of light inputcouplers are used to direct light into the side of a lightguide region.

In another embodiment, the folded coupling lightguides have lightcollimating edges, substantially linear edges, or light turning edges.In one embodiment, at least one selected from the group: array of foldedcoupling lightguides, light turning optical element, light collimatingoptical element, and light source are physically coupled to thenon-folded coupling lightguide. In another embodiment, folded couplinglightguides are physically coupled to each other and to the non-foldedcoupling lightguide by a pressure sensitive adhesive cladding layer andthe thickness of the unconstrained lightguide film including the lightemitting region and the array of coupling lightguides is less than oneof the following: 1.2 times, 1.5 times, 2 times, and 3 times thethickness of the array of coupling lightguides. By bonding the foldedcoupling lightguides only to themselves, the coupling lightguides (whenun-constrained) typically bend upward and increase the thickness of thearray due to the folded coupling lightguides not being physicallycoupled to a fixed or relatively constrained region. By physicallycoupling the folded coupling lightguides to a non-folded couplinglightguide, the array of coupling lightguides is physically coupled to aseparate region of the film which increases the stability and thusreduces the ability of the elastic energy stored from the bend to bereleased.

Coupling Lightguide Stack

In one embodiment, coupling lightguides extending from a lightguideregion in a film-based lightguide are folded at a 90 degree fold anglewith their ends stacked. In this embodiment, the radius of curvature foreach of the coupling lightguides is different due to the thickness ofeach of the coupling lightguides. In this embodiment, the radius ofcurvature for the nth coupling lightguide is determined by the equation:

${R_{n} = {R_{1} + {\frac{\left( {n - 1} \right)}{2}t}}},$where R₁ is an initial (smallest radius) coupling lightguide radius, andt is a thickness of the coupling lightguides.

The coupling lightguide stack can be configured in numerous ways tocompensate for the different radii of curvature. In one embodiment, thecoupling lightguides have one or more compensation features selectedfrom the group: staggered light input surfaces; coupling lightguidesoriented at an angle with respect to each other; varying lateral foldlocations; coupling lightguides angled in an oriented stack; non-uniformtension or torsion; a constant fold radius of curvature stack; and othercompensation techniques or features.

Sacrificial Coupling Lightguide

In one embodiment, the light input coupler includes a stacked array ofcoupling lightguides include at least one sacrificial couplinglightguide. In another embodiment, the film-based lightguide includes asacrificial coupling lightguide on one or both ends in an array ofcoupling lightguides extending from a lightguide region of the film. Inone embodiment, a sacrificial coupling lightguide is folded, stacked,and positioned to couple into the coupling lightguide in a totalinternal reflection condition a percentage of the total light flux fromthe light source at the light input coupler selected from the group: 0%,less than 1%, less than 2%, less than 5%, and less than 10%. In thisembodiment, for example, a wrap, housing, RPME, or other element of thelight emitting device can be physically or optically coupled to thesacrificial lightguide such that the light output of the light emittingdevice is not substantially reduced due to absorption or scattering oflight out of the top or bottom coupling lightguide in a stack ofcoupling lightguides. In one embodiment, one or two sacrificial couplinglightguides are cut to have a length such that when the array ofcoupling lightguides are folded and stacked, the distance from the endsof the one or two sacrificial coupling lightguides along the length ofthe folded, stacked coupling lightguides to the input surface of theremaining coupling lightguides in the array of coupling lightguides isgreater than one selected from the group: 1, 2, 5, 10, 15, 20, 40, 50,100, and 200 millimeters. In this embodiment, the light input surfaceformed by the end edges of the remaining, non-sacrificial couplinglightguides may be positioned to receive light from the light source andthe position of the ends of the one or two sacrificial couplinglightguides and/or a light blocking element disposed between the ends ofthe sacrificial coupling lightguides and the light source, prevents asignificant amount of flux (more than 5%, for example) from enteringinto the sacrificial coupling lightguides in a total internal reflectioncondition. In one embodiment, the one or two sacrificial couplinglightguides do not substantially “wet-out” (become optically coupledacross the interfaces such that the total internal reflection conditionis transferred from the first region into the second region) with theiradjacent coupling lightguides in the stack. In this embodiment, an airgap between the one or two sacrificial coupling lightguides can preventthe sacrificial coupling lightguides from transferring or de-couplingthe light out of their adjacent coupling lightguides such that ahousing, RPME, or light absorbing wrap may be physically coupled, to thesacrificial coupling lightguides (for example, such as a light absorbingblack tape wrapped around the stack of coupling lightguides such that itadheres to the top and bottom sacrificial coupling lightguides) withoutconcern of light absorption since the light from the light source is notsubstantially propagating through the sacrificial coupling lightguides.In one embodiment the width of the sacrificial coupling lightguides arelarger than the width of the intermediate coupling lightguides in thestack of coupling lightguides. In this embodiment, the wider width ofthe sacrificial coupling lightguides can enable an adhesive wrap toextended around and over a top cover region and side cover region of thesacrificial lightguides without contacting one or more lateral edges ofthe intermediate coupling lightguides (leaving an air gap between thewrap and lateral edges) such that it does not absorb or de-couple lightfrom the top coupling lightguide and the lateral edges of one or moreintermediate coupling lightguides because the adhesive of the wrap isnot in contact with the top surface of the top coupling lightguide (itmay be in contact with the top sacrificial coupling lightguide whichdoes not include a significant light flux, if any) or the lateral edgesof the coupling lightguides. In one embodiment the width of thesacrificial coupling lightguides are larger than the widths of theintermediate coupling lightguides in the stack of coupling lightguidesand portions of the one or two sacrificial coupling lightguides are benttoward the lateral edges of the remaining coupling lightguides. In thisembodiment, for example, the bent regions of the sacrificial couplinglightguides can help prevent wet-out and de-coupling or absorption oflight from the top coupling lightguide outer surface and lateral edgesof the stack of intermediate coupling lightguides by providing anintermediate, non-wetting out layer that prevents optical coupling ofthe lateral edges with an element such as a light absorbing wrapadhesive, RPME, housing or other element. In one embodiment, the widersacrificial coupling lightguides are perforated in a region (such as alinear region defined laterally by the lateral edges of the stack ofintermediate coupling lightguides) such that the sacrificial couplinglightguides may be easily bent and a side cover region of their filmsurfaces are substantially parallel to the lateral edge surfaces of theintermediate coupling lightguides. In one embodiment, one or moresurfaces of the sacrificial coupling lightguides may be roughened orinclude surface relief features, regions, or layers such that thesurface relief features are positioned between the one or twosacrificial coupling lightguides and the lateral edges of theintermediate coupling lightguides or the outer (non-lateral edge)surfaces of the outer intermediate coupling lightguides adjacent the oneor two sacrificial coupling lightguides.

Light Mixing Region

In one embodiment, a light emitting device includes a light mixingregion disposed in an optical path between the light input coupler andthe lightguide region. The light mixing region can provide a region forthe light output from individual coupling lightguides to mix togetherand improve at least one of a spatial luminance uniformity, a spatialcolor uniformity, an angular color uniformity, an angular luminanceuniformity, an angular luminous intensity uniformity or any combinationthereof within a region of the lightguide or of the surface or output ofthe light emitting region or light emitting device. In one embodiment, awidth of the light mixing region is selected from a range from 0.1 mm(for small displays) to more than 10 feet (for large billboards). In oneembodiment, the light mixing region is the region disposed along anoptical path near the end region of the coupling lightguides whereinlight from two or more coupling lightguides may inter-mix andsubsequently travel to a light emitting region of the lightguide. In oneembodiment, the light mixing region is formed from the same component ormaterial as at least one of the lightguide, lightguide region, lightinput coupler, and coupling lightguides.

Width of the Light Mixing Region or Array of Coupling Lightguides

In one embodiment, the length of the array of coupling lightguidesand/or the light mixing region is longer than the light emitting regionor lightguide region in a direction parallel to the array direction ofthe coupling lightguides (perpendicular to the extended direction of thearray of coupling lightguides). In one embodiment, the array of couplinglightguides and/or the light mixing region extends past a lateral sideof the light emitting region in the direction parallel to the arraydirection of the coupling lightguides (the perpendicular to the extendeddirection of the coupling lightguides) by a distance selected from thegroup: greater than 1 millimeter; greater than 2 millimeters; greaterthan 4 millimeters; greater than 6 millimeters; greater than 10millimeters; greater than 15 millimeters; greater than 20 millimeters;greater than 50% of the average width of the coupling lightguides;greater than 100% of the average width of the coupling lightguides; andgreater than 1%, 2%, 5%, or 10% of the length of the light emittingregion in the direction parallel to the array direction of the couplinglightguides. In one embodiment, the array of coupling lightguides orlight mixing region extends past the lateral edge of the light emittingregion opposite the direction of the fold. In a further embodiment, thearray of coupling lightguides or light mixing region extends past thelateral side of the light emitting region in the direction of the fold.In one embodiment, more light can be introduced into the edge region(defined as the region of the light emitting area within 10% of thelateral edge) by extending the array of coupling lightguides past thelateral edge of the light emitting region and/or extending the lightmixing region past the lateral edge of the light emitting region. In afurther embodiment, a lateral edge of the light mixing region, a lateraledge of one or more coupling lightguides, or an internal light directingedge is oriented at a first extended orientation angle to the extendeddirection of the coupling lightguides to direct light from the extendedregion of the array of coupling lightguides or the light mixing regiontoward the light emitting region of the film-based lightguide. In oneembodiment, the first extended orientation angle is greater than oneselected from the group: 0, 2, 5, 10, 20, 30, 45, and 60 degrees. Forexample, in one embodiment, the array of coupling lightguides includes acoupling lightguide that extends past the far lateral edge (the edgefurthest from the light source) of the light emitting area and the lightmixing region includes a lateral edge with an extended orientation angleof 30 degrees. In this embodiment, the far coupling lightguides arelonger in length, and thus more light is absorbed through the material.One method of compensation for the light flux difference reaching thefar edge region of the light emitting area due to the longer path lengthof light traveling toward the far edge region of the light emitting areais to add an additional coupling lightguide that can receive adistributed portion of the light from the light source and direct itinto the far edge region of the light emitting area by an angled lateraledge in the extended coupling lightguide, the light mixing region, or aninternal light directing edge.

Housing or Holding Device for Light Input Coupler

In one embodiment, a light emitting device includes a housing or holdingdevice that holds or includes at least part of a light input coupler andlight source. The housing or holding device may house or contain withinat least one selected from the group: light input coupler, light source,coupling lightguides, lightguide, optical components, electricalcomponents, heat sink or other thermal components, attachmentmechanisms, registration mechanisms, folding mechanisms devices, andframes. The housing or holding device may include a plurality ofcomponents or any combination of the aforementioned components. Thehousing or holding device may serve one or more of functions selectedfrom the group: protect from dust and debris contamination, provideair-tight seal, provide a water-tight seal, house or contain components,provide a safety housing for electrical or optical components, assistwith the folding or bending of the coupling lightguides, assist in thealignment or holding of the lightguide, coupling lightguide, lightsource or light input coupler relative to another component, maintainthe arrangement of the coupling lightguides, recycle light (such as withreflecting inner walls), provide attachment mechanisms for attaching thelight emitting device to an external object or surface, provide anopaque container such that stray light does not escape through specificregions, provide a translucent surface for displaying indicia orproviding illumination to an object external to the light emittingdevice, include a connector for release and interchangeability ofcomponents, and provide a latch or connector to connect with otherholding devices or housings.

In one embodiment, the housing or holding device includes at least oneselected from the group: connector, pin, clip, latch, adhesive region,clamp, joining mechanism, and other connecting element or mechanicalmeans to connect or hold the housing or holding device to anotherhousing or holding device, lightguide, coupling lightguide, film, strip,cartridge, removable component or components, an exterior surface suchas a window or automobile, light source, electronics or electricalcomponent, circuit board for the electronics or light source such as anLED, heat sink or other thermal control element, frame of the lightemitting device, and other component of the light emitting device.

In a another embodiment, the input ends and output ends of the couplinglightguides are held in physical contact with the relative positionmaintaining elements by at least one selected from the group: magneticgrips, mechanical grips, clamps, screws, mechanical adhesion, chemicaladhesion, dispersive adhesion, diffusive adhesion, electrostaticadhesion, vacuum holding, or an adhesive.

Curved or Flexible Housing

In another embodiment, the housing includes at least one curved surface.A curved surface can permit non-linear shapes or devices or facilitateincorporating non-planer or bent lightguides or coupling lightguides. Inone embodiment, a light emitting device includes a housing with at leastone curved surface wherein the housing includes curved or bent couplinglightguides. In another embodiment, the housing is flexible such that itmay be bent temporarily, permanently or semi-permanently. By using aflexible housing, for example, the light emitting device may be able tobe bent such that the light emitting surface is curved along with thehousing, the light emitting area may curve around a bend in a wall orcorner, for example. In one embodiment, the housing or lightguide may bebent temporarily such that the initial shape is substantially restored(bending a long housing to get it through a door for example). Inanother embodiment, the housing or lightguide may be bent permanently orsemi-permanently such that the bent shape is substantially sustainedafter release (such as when it is desired to have a curved lightemitting device to provide a curved sign or display, for example).

Housing Including a Thermal Transfer Element

In one embodiment, the housing includes a thermal transfer elementdisposed to transfer heat from a component within the housing to anouter surface of the housing. In another embodiment, the thermaltransfer element is one selected from the group: heat sink, metallic orceramic element, fan, heat pipe, synthetic jet, air jet producingactuator, active cooling element, passive cooling element, rear portionof a metal core or other conductive circuit board, thermally conductiveadhesive, or other component known to thermally conduct heat. In oneembodiment, the thermal transfer element has a thermal conductivity(W/(m·K)) greater than one selected from the group: 0.2, 0.5, 0.7, 1, 3,5, 50, 100, 120, 180, 237, 300, and 400. In another embodiment, a framesupporting the film-based lightguide (such as one that holds tension inthe film to maintain flatness) is a thermal transfer element. In oneembodiment, the light source is an LED and the LED is thermally coupledto the ballast or frame that is a thermal transfer element. In a furtherembodiment, a frame or ballast used to thermally transfer heat away fromthe light source and is also a housing for the light emitting device.

Low Contact Area Cover

In one embodiment, a low contact area cover is disposed between at leastone coupling lightguide and the exterior to the light emitting device.The low contact area cover or wrap provides a low surface area ofcontact with a region of the lightguide or a coupling lightguide and mayfurther provide at least one selected from the group: protection fromfingerprints, protection from dust or air contaminants, protection frommoisture, protection from internal or external objects that woulddecouple or absorb more light than the low contact area cover when incontact in one or more regions with one or more coupling lightguides,provide a means for holding or including at least one couplinglightguide, hold the relative position of one or more couplinglightguides, reflect light back through the lightguide, and prevent thecoupling lightguides from unfolding into a larger volume or contact witha surface that could de-couple or absorb light. In one embodiment, thelow contact area cover is disposed substantially around one or morecoupling lightguide stacks or arrays and provides one or more of thefunctions selected from the group: reducing the dust buildup on thecoupling lightguides, protecting one or more coupling lightguides fromfrustrated total internal reflection or absorption by contact withanother light transmitting or absorbing material, and preventing orlimiting scratches, cuts, dents, or deformities from physical contactwith other components or assemblers and/or users of the device.

In another embodiment, the low contact area cover is disposed betweenthe outer surface of the light emitting device and the regions of thecoupling lightguides disposed between the fold or bend region and thelightguide or light mixing region. In a further embodiment, the lowcontact area cover is disposed between the outer surface of the lightemitting device and the regions of the coupling lightguides disposedbetween the light input surface of the coupling lightguides and thelightguide or light mixing region. In another embodiment, the lowcontact area cover is disposed between the outer surface of the lightemitting device and a portion of the regions of the coupling lightguidesnot enclosed by a housing, protective cover, or other component disposedbetween the coupling lightguides and the outer surface of the lightemitting device. In one embodiment, the low contact area cover is thehousing, relative position maintaining element, or a portion of thehousing or relative positioning maintaining element. In one embodiment,the low contact area surface feature is a protrusion from a film,material, or layer. In another embodiment, the low contact area cover orwrap is disposed substantially around the light emitting device.

Film-Based Low Contact Area Cover

In one embodiment the low contact area cover is a film with at least oneof a lower refractive index than the refractive index of the outermaterial of the coupling lightguide disposed near the low contact areacover, and a surface relief pattern or structure on the surface of thefilm-based low contact area cover disposed near at least one couplinglightguide. In one embodiment, the low contact area includes convex orprotruding surface relief features disposed near at least one outersurface of at least one coupling lightguide and the average percentageof the area disposed adjacent to an outer surface of a couplinglightguide or the lightguide that is in physical contact with thesurface relief features is less than one of the following: 70%, 50%,30%, 10%, 5%, and 1%. In another embodiment, the low contact area coverincludes surface relief features adjacent and in physical contact with aregion of the film-based lightguide and the percentage of the region ofthe film-based lightguide (or light mixing region, or couplinglightguides) in contact with the low contact area cover is less than oneof the following: 70%, 50%, 30%, 10%, 5%, and 1%. In another embodiment,the low contact area cover includes surface relief features adjacent aregion of the film-based lightguide and the percentage of the area ofthe surface relief features that contact a region of the film-basedlightguide (or light mixing region, or coupling lightguides) when auniform planar pressure of 7 kilopascals is applied to the low contactarea cover is less than one of the following: 70%, 50%, 30%, 10%, 5%,and 1%. In one embodiment, the low contact area cover is a surfacerelief diffuser disposed in a backlight on the side of the film-basedlightguide opposite the light emitting side of the backlight such thatthe surface relief features are in contact with the film-basedlightguide. In one embodiment, the film-based lightguide is physicallycoupled to the low contact area cover that is physically coupled to arigid support or the housing of a backlight.

In one embodiment, a convex surface relief profile designed to have alow contact area with a surface of the coupling lightguide will at leastone selected from the group: extract, absorb, scatter, and otherwisealter the intensity or direction of a lower percentage of lightpropagating within the coupling lightguide than a flat surface of thesame material. In one embodiment, the surface relief profile is at leastone selected from the group: random, semi-random, ordered, regular inone or 2 directions, holographic, tailored, include cones, truncatedpolyhedrons, truncated hemispheres, truncated cones, truncated pyramids,pyramids, prisms, pointed shapes, round tipped shapes, rods, cylinders,hemispheres, and other geometrical shapes. In one embodiment, the lowcontact area cover material or film is at least one selected from thegroup: transparent, translucent, opaque, light absorbing, lightreflecting, substantially black, substantially white, has a diffusereflectance specular component included greater than 70%, has a diffusereflectance specular component included less than 70%, has an ASTM D1003luminous transmittance less than 30%, has an ASTM D1003 luminoustransmittance greater than 30%, absorbs at least 50% of the incidentlight, absorbs less than 50% of the incident light, has an electricalsheet resistance less than 10 ohms per square, and has an electricalsheet resistance greater than 10 ohms per square. In one embodiment, lowcontact area material has a diffuse reflectance measured in the di/0geometry according to ASTM E 1164-07 and ASTM E 179 greater than oneselected from the group: 70%, 80%, 85%, 90%, 95%, and 95%.

In another embodiment, the low contact area cover is a film with athickness less than one selected from the group: 600 microns, 500microns, 400 microns, 300 microns, 200 microns, 100 microns, and 50microns.

In another embodiment, the low contact area cover includes a materialwith an effective refractive index less than the core layer due tomicrostructures and/or nanostructures. For example, in one embodiment,the low contact area includes an aerogel or arrangement ofnano-structured materials disposed on a film that have an effectiverefractive index less than the core layer in the region near the corelayer. In one embodiment, the nano-structured material includes fibers,particles, or domains with an average diameter or dimension in the planeparallel to the core layer surface or perpendicular to the core layersurface less than one selected from the group: 1000, 500, 300, 200, 100,50, 20, 10, 5, and 2 nanometers. For example, in one embodiment, the lowcontact area cover is a coating or material including nanostructuredfibers, including polymeric materials such as, without limitation,cellulose, polyester, PVC, PTFE, polystyrene, PMMA, PDMS, or other lighttransmitting or partially light transmitting materials. In oneembodiment, the low contact area is a paper or similar sheet or film(such as a filter paper) including fibrous, micro-structured, ornano-structured materials or surfaces. In one embodiment, the lowcontact area material is a woven material. In another embodiment, thelow contact area material is non-woven material. In another embodiment,the low contact area cover is a substantially transparent or translucentlight transmitting film that includes “macro” surface features withaverage dimensions greater than 5 microns that have micro-structured,nanostructured, or fibrous materials or surface features disposed on orwithin the outer regions of the “macro” surface features. In oneembodiment, the “macro” surface features have an average dimension in afirst direction parallel to the core surface or perpendicular to thecore surface greater than one selected from the group: 5, 10, 15, 20,30, 50, 100, 150, 200, and 500 microns and the micro-structured,nanostructured, or fibrous materials or surface features have an averagedimension in the first direction less than one selected from the group:20, 10, 5, 2, 1, 0.5, 0.3, 0.1, 0.05, and 0.01 microns.

In this embodiment, the “macro” surface features can be patterned into asurface (such as by extrusion embossing or UV cured embossing) and theouter regions (outermost surfaces of the protruded regions that would bein contact with the core layer) can remain, be formed, coated,roughened, or otherwise modified to include micro-structured,nanostructured, or fibrous materials or surface features such that whenin contact with the core layer couple less light out of the core layerdue to the smaller surface area in contact with the core layer. In oneembodiment, by only coating the tips of the “macro” protrusions, forexample, less nanostructured material is needed than coating the entirelow contact area film or a planar film and the “valleys” or areas aroundthe “macro” protrusions may be light transmitting, transparent, ortranslucent. In another embodiment, the micro-structured,nanostructured, or fibrous materials or surface features disposed on orwithin the “macro” surface features create an effective lower refractiveindex region that functions as a cladding layer. In one embodiment, thelow contact area cover extracts less than one selected from the group:30%, 20%, 10%, 5%, 2%, and 1% of the light from the core region in atleast one region (or the entire region) of contact with the core layeror region adjacent the core layer. In another embodiment, the lowcontact area cover extracts more than one selected from the group: 1%,5%, 10%, 15%, and 20% of the light from the lightguide in the lightemitting region.

In one embodiment, the low contact area includes standoffs, posts, orother protrusions that provide a separation distance between the lowcontact area cover and the core layer. In one embodiment, the standoffs,posts, or other protrusions are disposed in one or more regions of thelow contact area cover selected from the group: the region adjacent thelight emitting region, the region adjacent the surface opposite thelight emitting surface, the region adjacent the light mixing region, theregion adjacent the light input coupler, the region adjacent thecoupling lightguides, in a pattern on one surface of the low contactarea cover, and in a pattern on both surfaces of the low contact areacover. In one embodiment, the standoffs, posts, or other protrusions ofthe low contact area cover have an average dimension in a directionparallel to the surface of the core layer or perpendicular to the corelayer greater than one selected from the group: 5, 10, 20, 50, 100, 200,500, and 1000 microns. In another embodiment, the aspect ratio (theheight divided by the average width in the plane parallel to the coresurface) is greater than one selected from the group: 1, 2, 5, 10, 15,20, 50, and 100.

In another embodiment, the low contact area cover is physically coupledto the lightguide or core layer in one or more regions selected from thegroup: an area around the light emitting region of the lightguide, aperiphery region of the lightguide that emits less than 5% of the totallight flux emitted from the lightguide, a region of the housing of theinput coupler, a cladded layer or region, a standoff region, a postregion, a protrusions region, a “macro” surface feature region, anano-structured feature region, a micro-structured feature region, and aplateau region disposed between valley regions by one or more selectedfrom the group: chemical bonds, physical bonds, adhesive layer, magneticattraction, electrostatic force, van der Waals force, covalent bonds,and ionic bonds. In another embodiment, the low contact area cover islaminated to the core layer.

In one embodiment, the low contact area cover is a sheet, film, orcomponent including one or more selected from the group: paper, fibrousfilm or sheet, cellulosic material, pulp, low-acidity paper, syntheticpaper, flashspun fibers, flashspun high-density polyethylene fibers, anda micro-porous film. In another embodiment, the film material of the lowcontact area cover or the area of the low contact area cover in contactwith the core layer of the lightguide in the light emitting regionincludes a material with a bulk refractive index or an effectiverefractive index in a direction parallel or perpendicular to the coresurface less than one selected from the group: 1.6, 1.55, 1.5, 1.45,1.41, 1.38, 1.35, 1.34, 1.33, 1.30, 1.25, and 1.20.

Wrap Around Low Contact Area Cover

In a further embodiment, the low contact area cover is the inner surfaceor physically coupled to a surface of a housing, holding device, orrelative position maintaining element. In a further embodiment, the lowcontact area cover is a film which wraps around at least one couplinglightguide such that at least one lateral edge and at least one lateralsurface is substantially covered such that the low contact area cover isdisposed between the coupling lightguide and the outer surface of thedevice.

In another embodiment, a film-based lightguide includes a low contactarea cover wrapped around a first group of coupling lightguides whereinthe low contact area cover is physically coupled to at least oneselected from the group: lightguide, lightguide film, light inputcoupler, lightguide, housing, and thermal transfer element by a lowcontact area cover physical coupling mechanism. In another embodiment,the light emitting device includes a first cylindrical tension roddisposed to apply tension to the low contact area cover film and holdthe coupling lightguides close together and close to the lightguide suchthat the light input coupler has a lower profile. In another embodiment,the low contact area cover can be pulled taught after physicallycoupling to at least one selected from the group: lightguide, lightguidefilm, light input coupler, lightguide, housing, thermal transferelement, and other element or housing by moving the first cylindricaltension rod away from a second tension bar or away from a physicalcoupling point of the mechanism holding the tension bar such as a brace.Other shapes and forms for the tension forming element may be used suchas a rod with a rectangular cross-section, a hemisphericalcross-section, or other element longer in a first direction capable ofproviding tension when translated or supporting tension when heldstationary relative to other components. In another embodiment, a firstcylindrical tension rod may be translated in a first direction toprovide tension while remaining in a brace region and the position ofthe cylindrical tension rod may be locked or forced to remain in placeby tightening a screw for example. In another embodiment, the tensionforming element and the brace or physical coupling mechanism forcoupling it to the another component of the light input coupler does notextend more than one selected from the group: 1 millimeter, 2millimeters, 3 millimeters, 5 millimeters, 7 millimeters and 10millimeters past at least one edge of the lightguide in the directionparallel to the longer dimension of the tension forming element.

In one embodiment, the low contact area cover substantially wraps aroundthe film-based lightguide in one or more planes. In another embodiment,the low contact area cover substantially wraps around the film-basedlightguide and one or more light input couplers. For example, in oneembodiment the low contact area cover wraps around two input couplersdisposed along opposite sides of a film based lightguide and the lightemitting region of the lightguide disposed between the light inputcouplers. The other edges of the low contact cover may be sealed,bonded, clamped together or another material or enclosing method mayseal or provide a barrier at the opposite edges to prevent dust or dirtcontamination, for example. In this embodiment, for example, a backlightmay include a substantially air-tight sealed film-based lightguide (andsealed coupling lightguides within the light input coupler) that doesnot have one or more cladding regions and is substantially protectedfrom scratches or dust during assembly or use that could causenon-uniformities or reduce luminance or optical efficiency.

Properties of the Wrap Around the Coupling Lightguides

In one embodiment, a wrap includes a low contact area cover wrappedaround at least one surface of a stack of coupling lightguides. Inanother embodiment, the wrap includes a material wrapped around theRPME. In one embodiment, the wrap is a low contact area cover. In afurther embodiment, the wrap is a material or film that extends acrossat least one surface of a stack of coupling lightguides.

In one embodiment, the wrap has a Young's modulus less than one selectedfrom the group: 10, 8, 6, 4, 2, 1, 0.5, and 0.1 gigapascals. In anotherembodiment, the wrap can be sufficiently stretched around the stack ofcoupling lightguides such that it conforms to one or more of the outersurfaces of the stack under tension in the wrapping operation. Inanother embodiment, the wrap is plastically deformable. In oneembodiment, the wrap material has a yield strength in one or moreregions less than one selected from the group: 200, 100, 90, 75, 50, 40,30, 20, and 10 megapascals. In one embodiment, the wrap has perforationsin one or more regions that reduce the yield strength in those regions.For example, in one embodiment, the wrap material is a thin aluminumsheet with one or more linear perforations corresponding to one or morecorners of the stack of coupling lightguides such that the aluminumsheet may be easily bent around one or more corners of the stack. In oneembodiment, the wrap material includes one or more materials selectedfrom the group: tape, metal sheet, aluminum sheet, stainless steelsheet, copper sheet, cellulose, polymer film, silicone, polyethylene,polypropylene, polyester, polycarbonate, polymethyl methacrylate,polyimide, fluoropolymer, polymethyl pentene, elastomer, and a rubber.In one embodiment, the wrap material is non-homogeneous. For example, inone embodiment, the wrap includes a region including a pressuresensitive adhesive and one or more regions without a pressure sensitiveadhesive. For example, in one embodiment, the region of the wrapcorresponding to the regions adjacent the lateral edges of the stack ofcoupling lightguides does not have an adhesive in order to prevent orreduce light coupling from the edges into the wrap material. In oneembodiment, the wrap is a stamped metal or plastic component. In thisembodiment, the stamped metal or plastic component may include one ormore curved edges to prevent the edge from cutting or tearing thelightguide. In one embodiment, the wrap includes a metal and dissipatesheat from one or more light sources, an intermediate element thermallycoupled to the light source (such as a metal core substrate to which anLED is thermally coupled), one or more coupling lightguides, thelightguide region, the light mixing region, an optical element, a heatsink, a heat pipe, or a thermally conductive element in the lightemitting device.

In another embodiment, the wrap includes one or more alignment holes.The alignment holes may be used, for example, to align the wrap with thefilm-based lightguide, the stack of coupling lightguides, or anintermediate component that is physical coupled (and possiblyregistered) to the lightguide. In another embodiment, the wrap includesone or more tabs that facilitate the holding and/or wrapping of the wrapmaterial. In one embodiment, the tab regions are perforated such thatthey may be removed after the wrap material is wrapped around the stackof coupling lightguides, or folded behind or in front of a region of thewrap or light emitting device (and possibly adhered to the region). Inone embodiment the wrap material is separated from one or more lateraledges of the coupling lightguides along at least one side of a stack ofcoupling lightguides by an air gap. In one embodiment, the air gapallows more light to propagate through the coupling lightguides withoutcoupling into and/or being absorbed into the wrap material. In oneembodiment, the wrap couples out light (and possibly absorbs the light)propagating within the coupling lightguides, light mixing region, orlightguide region at high angles from the optical axis that would becoupled directly into a display and create a non-uniform bright regionif the film based lightguide was adhered to the display using anadhesive with a similar or lower refractive index as the adhesivematerial of the wrap. In another embodiment, the wrap provides one ormore of the following functions: protection of one or more surfaces ofthe coupling lightguides or film-based lightguide from scratches or dustor other material contamination; holding the stack of couplinglightguides together and/or holding one or more coupling lightguide in aposition relative to a region of the film-based lightguide; andabsorbing stray light from the light source, or stray or undesiredreflection or transmission out of one or more coupling lightguides orregions of the lightguide.

In one embodiment, the wrap is a conformal coating or material. Forexample, in one embodiment the wrap is a conformal low refractive indexsilicone coating that is coated over at least one surface of at leastone light input coupler element selected from the group: one or morecoupling lightguides, the stack of coupling lightguides, the RPME, thelight source, a light collimating optical element, a circuit board forthe light source, and the housing of the light input coupler. In oneembodiment, the conformal material is molded onto one or more surfacesof the one or more of the aforementioned light input coupler elements.For example, in one embodiment, the wrap is a low refractive indexconformal fluoropolymer coating spray coated or dip coated onto one ormore of the aforementioned light input coupler elements, such as thestack of coupling lightguides. In another embodiment, the conformal wrapmaterial is vacuum thermoformed or injection molded onto the surface ofone or more of the aforementioned light input coupler elements. Inanother embodiment, the wrap includes a UV curable material that isvacuum pulled into a mold around one or more light input couplerelements and subsequently cured or cross-linked by heat or UV radiation.In one embodiment, one or more side walls or surfaces of the mold isdefined by an inner surface region of the housing for the light inputcoupler. For example, in one embodiment, a black plastic light inputcoupler housing with an opening or gate is positioned around the stackof coupling lightguides and a low refractive index silicone wrapmaterial flows through the aperture or gate and substantially fills theinterior volume and subsequently cures, hardens, or sets. In anotherembodiment, in addition to providing a wrap function, the injectedconformal coating material forms a light collimating optical element ora light redirecting optical element positioned between the light sourceand the light input surface. In one embodiment, a portion of thehousing, the light input coupler, or a removable mold provides the mold(or a portion of the mold) for the optical element formed from the wrapmaterial.

In one embodiment, after the wrap material is wrapped around the stackof coupling lightguides, the RPME is removed. In one embodiment, theadhesive strength or modulus of the wrap is sufficient to hold the stackof coupling lightguides together. In one embodiment, the mold for aconformal coating maintains the relative positions of the stack ofcoupling lightguides after the RPME is removed while the coating isinjected into the mold (or a material is vacuum thermoformed over thestack, for example). In one embodiment, the wrap material maintains therelative positions of the coupling lightguides after curing,solidifying, or wrapping. In one embodiment, the stack of couplinglightguides comprise an adhesive in contact with at least one outersurface and the wrap is adhered to one or more coupling lightguidesusing the adhesive. In one embodiment, the wrap comprises a thin metalbent around at least two sides of the stack of coupling lightguides. Inone embodiment, the wrap comprises a thin sheet of metal (such as asheet of aluminum less than 0.4 mm thick) bent around four sides of thestack of coupling lightguides. In this embodiment, the wrap may comprisephysical attachment features that enable it to be physically coupled tothe relative position maintaining element such as holes in the sheetmetal that can snap over protrusions in the relative positionmaintaining element or extensions in the sheet metal that extend outwardfrom a slot in the relative position maintaining element.

In one embodiment, the wrap includes a polymer and an adhesive or ametal and adhesive. In another embodiment, the wrap includes a flatlower surface, a flat upper surface, and two or more connecting supportsbetween the upper surface and the lower surface along one or both sidesadjacent the lateral edges of the stacked array of coupling lightguides.In one embodiment, the connecting supports have a curved surface regionpositioned adjacent the lateral edges of the stack of couplinglightguides such that the area of contact is minimized. In oneembodiment, the connecting supports are rod shaped. In anotherembodiment, the connecting supports have a polygonal, arcuate,semicircular, annulus, or a portion of an annulus cross-sectional shape.

Low Hardness Low Contact Area Cover

In another embodiment, the low contact area cover has an ASTM D3363pencil hardness under force from a 300 gram weight less than the outersurface region of the coupling lightguide disposed near the low contactarea cover. In one embodiment, the low contact area cover includes asilicone, polyurethane, rubber, or thermoplastic polyurethane with asurface relief pattern or structure. In a further embodiment, the ASTMD3363 pencil hardness under force from a 300 gram weight of the lowcontact area cover is at least 2 grades less than the outer surfaceregion of the coupling lightguide disposed near the low contact areacover. In another embodiment, the low contact area cover has an ASTM D3363 pencil hardness less than one selected from the group: 5H, 4H, 3H,2H, H, and F.

Cladding Layer

In one embodiment, at least one of the light input coupler, couplinglightguide, light mixing region, lightguide region, and lightguideincludes a cladding layer optically coupled to at least one surface. Acladding region, as used herein, is a layer optically coupled to asurface wherein the cladding layer includes a material with a refractiveindex, n_(clad), less than the refractive index of the material, n_(m),of the surface to which it is optically coupled. In a one embodiment,the average thickness of one or both cladding layers of the lightguideis less than one selected from the group: 100 microns, 60 microns, 30microns, 20 microns, 10 microns, 6 microns, 4 microns, 2 microns, 1micron, 0.8 microns, 0.5 microns, 0.3 microns, and 0.1 microns. In oneembodiment, the cladding layer includes an adhesive such as asilicone-based adhesive, acrylate-based adhesive, epoxy, radiationcurable adhesive, UV curable adhesive, or other light transmittingadhesive. Fluoropolymer materials may be used as a low refractive indexcladding material. In one embodiment, the cladding region is opticallycoupled to one or more of the following: a lightguide, a lightguideregion, a light mixing region, one surface of the lightguide, twosurfaces of the lightguide, a light input coupler, coupling lightguides,and an outer surface of the film. In another embodiment, the cladding isdisposed in optical contact with the lightguide, the lightguide region,or a layer or layers optically coupled to the lightguide and thecladding material is not disposed on one or more coupling lightguides.

In one embodiment, the cladding is one selected from the group: methylbased silicone pressure sensitive adhesive, fluoropolymer material(applied using a coating including a fluoropolymer substantiallydissolved in a solvent), and a fluoropolymer film. The cladding layermay be incorporated to provide a separation layer between the core orcore part of a lightguide region and the outer surface to reduceundesirable out-coupling (for example, frustrated totally internallyreflected light by touching the film with an oily finger) from the coreor core region of a lightguide. Components or objects such as additionalfilms, layers, objects, fingers, dust etc. that come in contact oroptical contact directly with a core or core region of a lightguide maycouple light out of the lightguide, absorb light or transfer the totallyinternally reflected light into a new layer. By adding a cladding layerwith a lower refractive index than the core, a portion of the light willtotally internally reflect at the core-cladding layer interface.Cladding layers may also be used to provide the benefit of at least oneof increased rigidity, increased flexural modulus, increased impactresistance, anti-glare properties, provide an intermediate layer forcombining with other layers such as in the case of a claddingfunctioning as a tie layer or a base or substrate for an anti-reflectioncoating, a substrate for an optical component such as a polarizer,liquid crystal material, increased scratch resistance, provideadditional functionality (such as a low-tack adhesive to bond thelightguide region to another element, a window “cling type” film such asa highly plasticized PVC). The cladding layer may be an adhesive, suchas a low refractive index silicone adhesive which is optically coupledto another element of the device, the lightguide, the lightguide region,the light mixing region, the light input coupler, or a combination ofone or more of the aforementioned elements or regions. In oneembodiment, a cladding layer is optically coupled to a rear polarizer ina backlit liquid crystal display. In another embodiment, the claddinglayer is optically coupled to a polarizer or outer surface of afront-lit display such as an electrophoretic display, e-book display,e-reader display, MEMs type display, electronic paper displays such asE-Ink® display by E Ink Corporation, reflective or partially reflectiveLCD display, cholesteric display, or other display capable of beingilluminated from the front. In another embodiment, the cladding layer isan adhesive that bonds the lightguide or lightguide region to acomponent such as a substrate (glass or polymer), optical element (suchas a polarizer, retarder film, diffuser film, brightness enhancementfilm, protective film (such as a protective polycarbonate film), thelight input coupler, coupling lightguides, or other element of the lightemitting device. In one embodiment, the cladding layer is separated fromthe lightguide or lightguide region core layer by at least oneadditional layer or adhesive.

In one embodiment, the cladding region is optically coupled to one ormore surfaces of the light mixing region to prevent out-coupling oflight from the lightguide when it is in contact with another component.In this embodiment, the cladding also enables the cladding and lightmixing region to be physically coupled to another component.

Cladding Location

In one embodiment, the cladding region is optically coupled to at leastone selected from the group: lightguide, lightguide region, light mixingregion, one surface of the lightguide, two surfaces of the lightguide,light input coupler, coupling lightguides, and an outer surface of thefilm. In another embodiment, the cladding is disposed in optical contactwith the lightguide, lightguide region, or layer or layers opticallycoupled to the lightguide and the cladding material is not disposed onone or more coupling lightguides. In one embodiment, the couplinglightguides do not include a cladding layer between the core regions inthe region near the light input surface or light source. In anotherembodiment, the core regions may be pressed or held together and theedges may be cut and/or polished after stacking or assembly to form alight input surface or a light turning edge that is flat, curved, or acombination thereof. In another embodiment, the cladding layer is apressure sensitive adhesive and the release liner for the pressuresensitive adhesive is selectively removed in the region of one or morecoupling lightguides that are stacked or aligned together into an arraysuch that the cladding helps maintain the relative position of thecoupling lightguides relative to each other. In another embodiment, theprotective liner is removed from the inner cladding regions of thecoupling lightguides and is left on one or both outer surfaces of theouter coupling lightguides.

In one embodiment, a cladding layer is disposed on one or both oppositesurfaces of the light emitting region and is not disposed between two ormore coupling lightguides at the light input surface. For example, inone embodiment, a mask layer is applied to a film based lightguidecorresponding to the end regions of the coupling lightguides that willform the light input surface after cutting (and possibly the couplinglightguides) and the film is coated on one or both sides with a lowrefractive index coating. In this embodiment, when the mask is removedand the coupling lightguides are folded (using, for example a relativeposition maintaining element) and stacked, the light input surface canincludes core layers without cladding layers and the light emittingregion can include a cladding layer (and the light mixing region mayalso include a cladding and/or light absorbing region), which isbeneficial for optical efficiency (light is directed into the claddingat the input surface) and in applications such as film-based frontlightsfor reflective or transflective displays where a cladding may be desiredin the light emitting region.

In another embodiment, the protective liner of at least one outersurface of the outer coupling lightguides is removed such that the stackof coupling lightguides may be bonded to one of the following: a circuitboard, a non-folded coupling lightguide, a light collimating opticalelement, a light turning optical element, a light coupling opticalelement, a flexible connector or substrate for a display or touchscreen,a second array of stacked coupling lightguides, a light input couplerhousing, a light emitting device housing, a thermal transfer element, aheat sink, a light source, an alignment guide, a registration guide orcomponent including a window for the light input surface, and anysuitable element disposed on and/or physically coupled to an element ofthe light input surface or light emitting device. In one embodiment, thecoupling lightguides do not include a cladding region on either planarside and optical loss at the bends or folds in the coupling lightguidesis reduced. In another embodiment, the coupling lightguides do notinclude a cladding region on either planar side and the light inputsurface input coupling efficiency is increased due to the light inputsurface area having a higher concentration of lightguide receivedsurface relative to a lightguide with at least one cladding.

In one embodiment, the cladding on at least one surface of thelightguide is applied (such as coated or co-extruded) and the claddingon the coupling lightguides is subsequently removed. In a furtherembodiment, the cladding applied on the surface of the lightguide (orthe lightguide is applied onto the surface of the cladding) such thatthe regions corresponding to the coupling lightguides do not have acladding. For example, the cladding material could be extruded or coatedonto a lightguide film in a central region wherein the outer sides ofthe film will include coupling lightguides. Similarly, the cladding maybe absent on the coupling lightguides in the region disposed in closeproximity to one or more light sources or the light input surface.

In one embodiment, two or more core regions of the coupling lightguidesdo not include a cladding region between the core regions in a region ofthe coupling lightguide disposed within a distance selected from thegroup: 1 millimeter, 2 millimeters, 4 millimeters, and 8 millimetersfrom the light input surface edge of the coupling lightguides. In afurther embodiment, two or more core regions of the coupling lightguidesdo not include a cladding region between the core regions in a region ofthe coupling lightguide disposed within a distance selected from thegroup: 10%, 20%, 50%, 100%, 200%, and 300% of the combined thicknessesof the cores of the coupling lightguides disposed to receive light fromthe light source from the light input surface edge of the couplinglightguides. In one embodiment, the coupling lightguides in the regionproximate the light input surface do not include cladding between thecore regions (but may include cladding on the outer surfaces of thecollection of coupling lightguides) and the coupling lightguides areoptically coupled together with an index-matching adhesive or materialor the coupling lightguides are optically bonded, fused, orthermo-mechanically welded together by applying heat and pressure. In afurther embodiment, a light source is disposed at a distance to thelight input surface of the coupling lightguides less than one selectedfrom the group: 0.5 millimeter, 1 millimeter, 2 millimeters, 4millimeters, and 6 millimeters and the dimension of the light inputsurface in the first direction parallel to the thickness direction ofthe coupling lightguides is greater than one selected from the group:100%, 110%, 120%, 130%, 150%, 180%, and 200% the dimension of the lightemitting surface of the light source in the first direction. In anotherembodiment, disposing an index-matching material between the coreregions of the coupling lightguides or optically coupling or boding thecoupling lightguides together in the region proximate the light sourceoptically couples at least one selected from the group: 10%, 20%, 30%,40%, and 50% more light into the coupling lightguides than would becoupled into the coupling lightguides with the cladding regionsextending substantially to the light input edge of the couplinglightguide. In one embodiment, the index-matching adhesive or materialhas a refractive index difference from the core region less than oneselected from the group: 0.1, 0.08, 0.05, and 0.02. In anotherembodiment, the index-matching adhesive or material has a refractiveindex greater by less than one selected from the group: 0.1, 0.08, 0.05,and 0.02 the refractive index of the core region. In a furtherembodiment, a cladding region is disposed between a first set of coreregions of coupling lightguides for a second set of coupling lightguidesan index-matching region is disposed between the core regions of thecoupling lightguides or they are fused together. In a furtherembodiment, the coupling lightguides disposed to receive light from thegeometric center of the light emitting area of the light source within afirst angle of the optical axis of the light source have claddingregions disposed between the core regions, and the core regions atangles larger than the first angle have index-matching regions disposedbetween the core regions of the coupling lightguides or they are fusedtogether. In one embodiment, the first angle is selected from the group:10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, and 60degrees. In the aforementioned embodiments, the cladding region may be alow refractive index material or air. In a further embodiment, the totalthickness of the coupling lightguides in the region disposed to receivelight from a light source to be coupled into the coupling lightguides isless than n times the thickness of the lightguide region where n is thenumber of coupling lightguides. In a further embodiment, the totalthickness of the coupling lightguides in the region disposed to receivelight from a light source to be coupled into the coupling lightguides issubstantially equal to n times the thickness of the lightguide layerwithin the lightguide region.

Cladding Thickness

In a one embodiment, the average thickness of one or both claddinglayers of the lightguide is less than one selected from the group: 100microns, 60 microns, 30 microns, 20 microns, 10 microns, 6 microns, 4microns, 2 microns, 1 micron, 0.8 microns, 0.5 microns, 0.3 microns, and0.1 microns.

In a total internal reflection condition, the penetration depth, λ_(e)of the evanescent wave light from the denser region into the rarermedium from the interface at which the amplitude of the light in therarer medium is 1/e that at the boundary is given by the equation:

$\lambda_{e =}\frac{\lambda_{0}}{2{\pi\left\lbrack {\left( {n_{s}^{2}\left( {\sin\;\vartheta_{i}} \right)}^{2} \right) - n_{e}^{2}} \right\rbrack}^{\frac{1}{2}}}$where λ₀ is the wavelength of the light in a vacuum, n_(s) is therefractive index of the denser medium (core region) and n_(e) is therefractive index of the rarer medium (cladding layer) and θ_(i) is theangle of incidence to the interface within the denser medium. Theequation for the penetration depth illustrates that for many of theangular ranges above the critical angle, the light propagating withinthe lightguide does not need a very thick cladding thickness to maintainthe lightguide condition. For example, light within the visiblewavelength range of 400 nanometers to 700 nanometers propagating withina silicone film-based core region of refractive index 1.47 with afluoropolymer cladding material with a refractive index of 1.33 has acritical angle at about 65 degrees and the light propagating between 70degrees and 90 degrees has a 1/e penetration depth, λ_(e), less thanabout 0.3 microns. In this example, the cladding region thickness can beabout 0.3 microns and the lightguide will significantly maintain visiblelight transmission in a lightguide condition from about 70 degrees and90 degrees from the normal to the interface. In another embodiment, theratio of the thickness of the core layer to one or more cladding layersis greater than one selected from the group: 2, 4, 6, 8, 10, 20, 30, 40,and 60 to one. In one embodiment, a high core to cladding layerthickness ratio where the cladding extends over the light emittingregion and the coupling lightguides enables more light to be coupledinto the core layer at the light input surface because the claddingregions represent a lower percentage of the surface area at the lightinput surface.

In one embodiment, the cladding layer includes an adhesive such as asilicone-based adhesive, acrylate-based adhesive, epoxy, radiationcurable adhesive, UV curable adhesive, or other light transmittingadhesive.

Cladding Layer Materials

Fluoropolymer materials may be used as a low refractive index claddingmaterial and may be broadly categorized into one of two basic classes. Afirst class includes those amorphous fluoropolymers includinginterpolymerized units derived from vinylidene fluoride (VDF) andhexafluoropropylene (HFP) and optionally tetrafluoroethylene (TFE)monomers. Examples of such are commercially available from 3M Company asDyneon™ Fluoroelastomer FC 2145 and FT 2430. Additional amorphousfluoropolymers that can be used in embodiments are, for example,VDF-chlorotrifluoroethylene copolymers. One suchVDF-chlorotrifluoroethylene copolymer is commercially known as Kel-F™3700, available from 3M Company. As used herein, amorphousfluoropolymers are materials that include essentially no crystallinityor possess no significant melting point as determined for example bydifferential scanning caloriometry (DSC). For the purpose of thisdiscussion, a copolymer is defined as a polymeric material resultingfrom the simultaneous polymerization of two or more dissimilar monomersand a homopolymer is a polymeric material resulting from thepolymerization of a single monomer.

The second significant class of fluoropolymers useful in an embodimentare those homo and copolymers based on fluorinated monomers such as TFEor VDF which have a crystalline melting point such as polyvinylidenefluoride (PVDF, available commercially from 3M company as Dyneon™ PVDF,or more preferable thermoplastic copolymers of TFE such as those basedon the crystalline microstructure of TFE-HFP-VDF. Examples of suchpolymers are those available from 3M under the trade name Dyneon™Fluoroplastics THV™ 200.

In one embodiment, the cladding material is birefringent and therefractive index in at least a first direction is less than refractiveindex of the lightguide region, lightguide core, or material to which itis optically coupled.

Collimated light propagating through a material may be reduced inintensity after passing through the material due to scattering(scattering loss coefficient), absorption (absorption coefficient), or acombination of scattering and absorption (attenuation coefficient). Inone embodiment, the cladding includes a material with an averageabsorption coefficient for collimated light less than one selected fromthe group: 0.03 cm⁻¹, 0.02 cm⁻¹, 0.01 cm⁻¹, and 0.005 cm⁻¹ over thevisible wavelength spectrum from 400 nanometers to 700 nanometers. Inanother embodiment, the cladding includes a material with an averagescattering loss coefficient for collimated light less than one selectedfrom the group: 0.03 cm⁻¹, 0.02 cm⁻¹, 0.01 cm⁻¹, and 0.005 cm⁻¹ over thevisible wavelength spectrum from 400 nanometers to 700 nanometers. Inanother embodiment, the cladding includes a material with an averageattenuation coefficient for collimated light less than one selected fromthe group: 0.03 cm⁻¹, 0.02 cm⁻¹, 0.01 cm⁻¹, and 0.005 cm⁻¹ over thevisible wavelength spectrum from 400 nanometers to 700 nanometers.

In a further embodiment, a lightguide includes a hard cladding layerthat substantially protects a soft core layer (such as a soft siliconeor silicone elastomer).

In one embodiment, a lightguide includes a core material with aDurometer Shore A hardness (JIS) less than 50 and at least one claddinglayer with a Durometer Shore A hardness (JIS) greater than 50. In oneembodiment, a lightguide includes a core material with an ASTM D638-10Young's Modulus less than 2 MPa and at least one cladding layer with anASTM D638-10 Young's Modulus greater than 2 MPa at 25 degrees Celsius.In another embodiment, a lightguide includes a core material with anASTM D638-10 Young's Modulus less than 1.5 MPa and at least one claddinglayer with an ASTM D638-10 Young's Modulus greater than 2 MPa at 25degrees Celsius. In a further embodiment, a lightguide includes a corematerial with an ASTM D638-10 Young's Modulus less than 1 MPa and atleast one cladding layer with an ASTM D638-10 Young's Modulus greaterthan 2 MPa at 25 degrees Celsius.

In one embodiment, a lightguide includes a core material with an ASTMD638-10 Young's Modulus less than 2 MPa and the lightguide film has anASTM D638-10 Young's Modulus greater than 2 MPa at 25 degrees Celsius.In another embodiment, a lightguide includes a core material with anASTM D638-10 Young's Modulus less than 1.5 MPa and the lightguide filmhas an ASTM D638-10 Young's Modulus greater than 2 MPa at 25 degreesCelsius. In one embodiment, a lightguide includes a core material withan ASTM D638-10 Young's Modulus less than 1 MPa and the lightguide filmhas an ASTM D638-10 Young's Modulus greater than 2 MPa at 25 degreesCelsius.

In another embodiment, the cladding includes a material with aneffective refractive index less than the core layer due tomicrostructures or nanostructures. In another embodiment, the claddinglayer includes an a porous region including air or other gas or materialwith a refractive index less than 1.2 such that the effective refractiveindex of the cladding layer is than that of the material around theporous regions. For example, in one embodiment, the cladding layer is anaerogel or arrangement of nano-structured materials disposed on the corelayer that creates a cladding layer with an effective refractive indexless than the core layer. In one embodiment, the nano-structuredmaterial includes fibers, particles, or domains with an average diameteror dimension in the plane parallel to the core layer surface orperpendicular to the core layer surface less than one selected from thegroup: 1000, 500, 300, 200, 100, 50, 20, 10, 5, and 2 nanometers. Forexample, in one embodiment, the cladding layer is a coating includingnanostructured fibers, including polymeric materials such as, withoutlimitation, cellulose, polyester, PVC, PTFE, polystyrene, PMMA, PDMS, orother light transmitting or partially light transmitting materials. Inanother embodiment, materials that normally scattering too much light inbulk form (such as HDPE or polypropylene) to be used as a core orcladding material for lightguide lengths greater than 1 meter (such asscattering greater than 10% of the light out of the lightguide over the1 meter length) are used in a nanostructured form. For example, in oneembodiment, the nanostructured cladding material on the film basedlightguide, when formed into a bulk solid form (such as a 200 micronthick homogeneous film formed without mechanically formed physicalstructures volumetrically or on the surface under film processingconditions designed to minimize haze substantially) has an ASTM hazegreater than 0.5%.

In a further embodiment, the microstructured or nanostructured claddingmaterial includes a structure that will “wet-out” or optically couplelight into a light extraction feature disposed in physical contact withthe microstructured or nanostructured cladding material. For example, inone embodiment, the light extraction feature includes nanostructuredsurface features that when in close proximity or contact with thenanostructured cladding region couple light from the cladding region. Inone embodiment, the microstructured or nanostructured cladding materialhas complementary structures to the light extraction feature structures,such as a male-female part or other simple or complex complementarystructures such that the effective refractive index in the regionincluding the two structures is larger than that of the cladding regionwithout the light extraction features.

Layers or Regions on Opposite Sides of the Lightguide of Materials withHigher and Lower Refractive Indexes

In one embodiment, a light emitting region of the film-based lightguidecomprises: a first layer or coating of a first material with a firstrefractive index optically coupled to a first surface of the film-basedlightguide in the light emitting region, a second layer or coating of asecond material with a second refractive index optically coupled to theopposite surface of the film-based lightguide in the light emittingregion, the second refractive index higher than the first refractiveindex, the second refractive index and the first refractive index lessthan the refractive index of the material in the core region of thelightguide. In this embodiment, light propagating within the core layeror region of the film-based lightguide in the light emitting region thatundergoes a low angle light redirection, such as by a low angledirecting feature, will preferentially leak or exit the lightguide onthe side with the second refractive index since it is higher than thefirst refractive index and the critical angle is higher. In thisembodiment, light deviating from angles higher than the critical angleto smaller angles from the thickness direction of the film will firstpass the total internal reflection interface on the side of the corelayer or region optically coupled to the cladding layer or region withthe higher refractive index.

Lightguide Configuration and Properties

In one embodiment, the thickness of the film, light redirecting opticalelement, reflective display, lightguide, and/or lightguide region iswithin a range of 0.005 mm to 0.5 mm. In another embodiment, thethickness of the film or lightguide is within a range of 0.025 mm (0.001inches) to 0.5 mm (0.02 inches). In a further embodiment, the thicknessof the film, lightguide and/or lightguide region is within a range of0.050 mm to 0.175 mm. In one embodiment, the thickness of the film,lightguide or lightguide region is less than 0.2 mm or less than 0.5 mm.In one embodiment, one or more of a thickness, a largest thickness, anaverage thickness, a greater than 90% of the entire thickness of thefilm, a lightguide, and a lightguide region is less than 0.2millimeters.

Optical Properties of the Lightguide or Light Transmitting Material

With regards to the optical properties of lightguides, light redirectingoptical element or region, light extraction film or region, or lighttransmitting materials for certain embodiments, the optical propertiesspecified herein may be general properties of the lightguide, the core,the cladding, or a combination thereof or they may correspond to aspecific region (such as a light emitting region, light mixing region,or light extracting region), surface (light input surface, diffusesurface, flat surface), and direction (such as measured normal to thesurface or measured in the direction of light travel through thelightguide).

Refractive Index of the Light Transmitting Material

In one embodiment, the core material of the lightguide has a higherrefractive index than the cladding material. In one embodiment, the coreis formed from a material with a refractive index (n_(D)) greater thanone selected from the group: 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, and 3.0. In anotherembodiment, the refractive index (n_(D)) of the cladding material isless than one selected from the group: 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5.

Surface Quality of Lightguide Core or Cladding

In one embodiment, the lightguide core and/or cladding region has anoptical quality surface finish and the loss in light flux propagatingthrough the lightguide due to the surface finish of the core region or acladding region is less than one selected from the group: 1%, 2%, 5%,10%, 20%, 30%, and 40%. The loss in light flux propagating through thelightguide due to surface finish can be measured by opticallyindex-matching with a fluid a rigid planar element with an opticallyflat surface finish to the core region or cladding region and measuringthe difference in the amount of light flux reaching the end of the newlycreated lightguide relative to the lightguide without the index matchedoptically smooth surface finish using an integrating sphere. In thismethod, the index matching fluid and the rigid planar element with anoptically smooth surface finish are optically non-scattering, opticallyhomogenous, have refractive indices within 0.001 units of the core orcladding region to which they are optically coupled, and have lowabsorption relative to the core and/or cladding material (any lowabsorption effects can be calculated and accounted for by using thecutback method). In this method, the optically smooth surface finish ofthe rigid planar element has a surface finish with at least one of thefollowing properties: an arithmetic mean roughness parameter, Ra (DIN4768 standard method), of 50 nanometers or less; a scratch-dig less than80 units, and a flatness value (peak to valley) less than 50 nanometers.

In one embodiment, the optical quality surface finish is a surface withone or more of the following surface properties: an arithmetic meanroughness parameter, Ra (DIN 4768 standard method), less than 500, 200,100, or 50 nanometers; a flatness value (peak to valley) less than 500,200, 100, or 50 nanometers; an RMS slope of the profile within thesampling length, RΔq, less than 1, 0.8, 0.6, 0.4, 0.2, 0.1, and 0.005milliradians; and an ASTM D523-08 gloss at 20 degrees greater than 80,90, 100, 110, 120, and 130 gloss units.

In another embodiment, the average haze of the lightguide measuredwithin at least one selected from the group: the light emitting region,the light mixing region, and the lightguide measured with a BYK Gardnerhaze meter is less than one selected from the group: 70%, 60%, 50%, 40%,30%, 20%, 10%, 5% and 3%. In another embodiment, the average clarity ofthe lightguide measured within at least one selected from the group: thelight emitting region, the light mixing region, and the lightguideaccording to the measurement procedure associated with ASTM D1003 with aBYK Gardner haze meter is greater than one selected from the group: 70%,80%, 88%, 92%, 94%, 96%, 98%, and 99%.

The effects of the surface roughness on the light propagating within thelightguide depend upon the number of surface reflections occurringduring the propagation. In one embodiment, the average number of surfacereflections from the top and bottom surfaces of the film-basedlightguide for light traveling within the central coupling lightguide(or average of the two central coupling lightguides) from the center ofthe coupling lightguide light input surface to the closest lightextraction feature in the light emitting region is greater than oneselected from the group: 1×10², 1×10³, 1×10⁴, 1×10⁵, 1×10⁶, 1×10⁷,1×10⁸, 1×10⁹, and 1×10¹⁰. The average number of reflections can becalculated using optical modeling software and averaging over the rangeof light propagation angles due to the incident light source outputprofile and position taking into account the proportional angulardistribution of the flux and the optical properties of the lightguidecore and cladding (which could be air), and any intermediate optics suchas collimating lenses or reflectors. In one embodiment, the reducedthickness of the lightguide core region in a film-based lightguideincreases the surface reflections and increases the requirements for alow surface roughness.

Edges of the Lightguide

In one embodiment, the edges of the lightguide or lightguide region arecoated, bonded to or disposed adjacent to a specularly reflectingmaterial, partially diffusely reflecting material, or diffuse reflectingmaterial. In one embodiment, the lightguide edges are coated with aspecularly reflecting ink including nano-sized or micron-sized particlesor flakes which reflect the light substantially specularly. In anotherembodiment, a light reflecting element (such as a specularly reflectingmulti-layer polymer film with high reflectivity) is disposed near thelightguide edge and is disposed to receive light from the edge andreflect it and direct it back into the lightguide. In anotherembodiment, the lightguide edges are rounded and the percentage of lightdiffracted from the edge is reduced. One method of achieving roundededges is by using a laser to cut the lightguide from a film and achieveedge rounding through control of the processing parameters (speed ofcut, frequency of cut, laser power, etc.). In another embodiment, theedges of the lightguide are tapered, angled serrated, or otherwise cutor formed such that light from a light source propagating within thecoupling lightguide reflects from the edge such that it is directed intoan angle closer to the optical axis of the light source, toward a foldedregion, toward a bent region, toward a lightguide, toward a lightguideregion, or toward the optical axis of the light emitting device. In afurther embodiment, two or more light sources are disposed to eachcouple light into two or more coupling lightguides including lightre-directing regions for each of the two or more light sources thatinclude first and second reflective surfaces which direct a portion oflight from the light source into an angle closer to the optical axis ofthe light source, toward a folded or bent region, toward a lightguideregion, toward a lightguide region, or toward the optical axis of thelight emitting device. In one embodiment, one or more edges of thecoupling lightguides, the lightguide, the light mixing region, or thelightguide region include a curve or arcuate profile in the region ofintersection between two or more surfaces of the film in a region.

Shape of the Lightguide

In one embodiment, at least a portion of the lightguide shape orlightguide surface is substantially planar, curved, cylindrical, aformed shape from a substantially planar film, spherical, partiallyspherical, angled, twisted, rounded, have a quadric surface, spheroid,cuboid, parallelepiped, triangular prism, rectangular prism, ellipsoid,ovoid, cone pyramid, tapered triangular prism, wave-like shape, and/orother known suitable geometrical solids or shapes. In one embodiment,the lightguide is a film formed into a shape by thermoforming or othersuitable forming techniques. In another embodiment, the film or regionof the film is tapered in at least one direction. In a furtherembodiment, a light emitting device includes a plurality of lightguidesand a plurality of light sources physically coupled or arranged together(such as tiled in a 1×2 array for example). In another embodiment, thesurface of the lightguide region of the film is substantially in theshape of a polygon, triangle, rectangle, square, trapezoid, diamond,ellipse, circle, semicircle, segment or sector of a circle, crescent,oval, annulus, alphanumeric character shaped (such as “U-shaped” or“T-shaped), or a combination of one or more of the aforementionedshapes. In another embodiment, the shape of the lightguide region of thefilm is substantially in the shape of a polyhedron, toroidal polyhedron,curved polyhedron, spherical polyhedron, rectangular cuboid, cuboid,cube, orthotope, stellation, prism, pyramid, cylinder, cone, truncatedcone, ellipsoid, paraboloid, hyperboloid, sphere, or a combination ofone or more of the aforementioned shapes.

Thickness of the Lightguide

In one embodiment, the thickness of the film, lightguide, lightguideregion, and/or light emitting region is within a range of 0.005 mm to0.5 mm. In another embodiment, the thickness of the film or lightguideis within a range of 0.025 mm (0.001 inches) to 0.5 mm (0.02 inches). Ina further embodiment, the thickness of the film, lightguide and/orlightguide region is within a range of 0.050 mm to 0.175 mm. In oneembodiment, the thickness of the film, lightguide or lightguide regionis less than 0.2 mm or less than 0.5 mm. In one embodiment, one or moreof a thickness, a largest thickness, an average thickness, greater than90% of the entire thickness of the film, a lightguide, and a lightguideregion is less than 0.2 millimeters. In one embodiment, the separationbetween the two surfaces of the core layer or region of the lightguidein the light emitting region deviates from the average separation byless than one selected from the group of 30%, 20%, 10%, and 5% of theaverage separation. In another embodiment, the separation distancebetween the two surfaces defining the total internal reflection surfacesfor the lightguide within the light emitting region deviates from theaverage separation distance by less than one selected from the group of30%, 20%, 10%, and 5% of the average separation distance. In oneembodiment, the average angle between the two surfaces defining thetotal internal reflection surfaces for the lightguide within the lightemitting region is less than one selected from the group of 10, 8, 6, 5,4, 3, 2, 1 and 0.5 degrees.

In one embodiment, the light emitting region tapers from a firstthickness at a first side of the light emitting region receiving lightfrom the light mixing region and/or the light input coupler to a secondthickness less than the first thickness at an opposite side of the lightemitting region along the direction of propagation of the light withinthe core region or layer of the lightguide in the light emitting region.In one embodiment, the average angle of the taper, the average anglebetween the two opposite layer surfaces or regions of the core layer ofthe lightguide from the first side to the second side, is less than oneselected from the group 10, 8, 6, 5, 4, 3, 2, 1, and 0.5 degrees.

In another embodiment the light emitting region comprises one or moreregions or layers optically coupled to the core region of the film-basedlightguide that increase the effective thickness of the lightguidedefined by the interfaces that define the total internal reflection oflight propagating from the first end to the opposite end of thelightguide in the light emitting region. In another embodiment, theratio of the average thickness of the light emitting region defined bythe interfaces that define the total internal reflection of lightpropagating from the first end to the opposite end of the light emittingregion to the average thickness of the light mixing region is greaterthan one or more selected from the group: 1, 2, 5, 10, 15, 20, 25, 30,40, and 50. In another embodiment the light emitting region comprisesone or more regions or layers optically coupled to the core region ofthe film-based lightguide that increase the effective thickness of thelightguide defined by the interfaces that define the total internalreflection of light propagating lightguide from the first end to theopposite end of the light emitting region.

In another embodiment, a light emitting device (such as a frontlight fora reflective display, for example) comprises a film-based lightguidewith the surfaces of the film defining a first lightguide and the firstlightguide is optically coupled to a light redirecting optical elementor other film and one or more surfaces of the light redirecting opticalelement or other film in combination with a surface of the firstlightguide define a second lightguide, wherein the second lightguide maycomprise the first lightguide. In this embodiment, the ratio of theaverage thickness of the light emitting region defined by the interfacesthat define the total internal reflection of light propagating from thefirst end to the opposite end of the light emitting region of the secondlightguide or first lightguide to the average thickness of the lightmixing region or the film is greater than one or more selected from thegroup: 1, 2, 5, 10, 15, 20, 25, 30, 40, and 50. In another embodiment,the ratio of the largest dimension of the light emitting area of thefirst lightguide or second lightguide in a plane orthogonal to thethickness direction of the light emitting surface or region of the lightemitting surface (parallel to a surface of the core layer) to theaverage thickness of the first lightguide or second lightguide in thelight emitting region is greater than one or more selected from thegroup: 1, 2, 5, 10, 15, 20, 25, 30, 40, 50.100, 200, 300, 500, 700,1000, and 2000.

In one embodiment, a reflective display comprises a lightguide whereinan effective thickness of the lightguide bounded by total internalreflection interfaces is increased for totally internally reflectedlight within the core layer that is frustrated by the plurality of lightextraction features such that it passes through the first cladding layerand totally internally reflects at one of the total internal reflectioninterfaces of a light redirecting optical element. In anotherembodiment, a light emitting device comprises a first lightguide havinga core layer having opposing surfaces with a thickness not greater thanabout 0.5 millimeters therebetween, the first lightguide defined by theopposing surfaces guiding light by total internal reflection, and asecond lightguide comprising the core layer, the second lightguidedefined by a second portion of the frustrated totally internallyreflected light from the first lightguide propagating by total internalreflection between a surface of the first lightguide and an area of thesurface of the light redirecting optical element between the lightredirecting features. In a further embodiment, a first lightguide and asecond lightguide comprise the core layer, the second lightguide definedby a portion of the frustrated totally internally reflected light fromthe first lightguide propagating by total internal reflection between asurface of the first lightguide and an area of a surface of the lightredirecting optical element, wherein the light redirecting features of alight redirecting optical element occupy less than 50% of the surface ofthe light redirecting optical element, the area of the surface of thelight redirecting element is defined between the light redirectingfeatures and reflects by total internal reflection a second portion ofthe frustrated totally internally reflected light from the lightextraction features back through a first cladding layer and into a corelayer of the first lightguide where it totally internally reflects fromthe surface of the first lightguide and is subsequently reflected by alight redirecting feature toward a reflective spatial light modulator.

Lightguide Material

In one embodiment, a light emitting device includes a lightguide orlightguide region formed from at least one light transmitting material.In one embodiment, the lightguide is a film includes at least one coreregion and at least one cladding region, each including at least onelight transmitting material. In one embodiment, the light transmittingmaterial is a thermoplastic, thermoset, rubber, polymer, hightransmission silicone, glass, composite, alloy, blend, silicone, orother suitable light transmitting material, or a combination thereof. Inone embodiment, a component or region of the light emitting deviceincludes a suitable light transmitting material, such as one or more ofthe following: cellulose derivatives (e.g., cellulose ethers such asethylcellulose and cyanoethylcellulose, cellulose esters such ascellulose acetate), acrylic resins, styrenic resins (e.g., polystyrene),polyvinyl-series resins [e.g., poly(vinyl ester) such as poly(vinylacetate), poly(vinyl halide) such as poly(vinyl chloride), polyvinylalkyl ethers or polyether-series resins such as poly(vinyl methylether), poly(vinyl isobutyl ether) and poly(vinyl t-butyl ether)],polycarbonate-series resins (e.g., aromatic polycarbonates such asbisphenol A-type polycarbonate), polyester-series resins (e.g.,homopolyesters, for example, polyalkylene terephthalates such aspolyethylene terephthalate and polybutylene terephthalate, polyalkylenenaphthalates corresponding to the polyalkylene terephthalates;copolyesters including an alkylene terephthalate and/or alkylenenaphthalate as a main component; homopolymers of lactones such aspolycaprolactone), polyamide-series resin (e.g., nylon 6, nylon 66,nylon 610), urethane-series resins (e.g., thermoplastic polyurethaneresins), copolymers of monomers forming the above resins [e.g., styreniccopolymers such as methyl methacrylate-styrene copolymer (MS resin),acrylonitrile-styrene copolymer (AS resin), styrene-(meth)acrylic acidcopolymer, styrene-maleic anhydride copolymer and styrene-butadienecopolymer, vinyl acetate-vinyl chloride copolymer, vinyl alkylether-maleic anhydride copolymer]. Incidentally, the copolymer may bewhichever of a random copolymer, a block copolymer, or a graftcopolymer.

Lightguide Material with Adhesive Properties

In another embodiment, the lightguide includes a material with at leastone selected from the group: chemical adhesion, dispersive adhesion,electrostatic adhesion, diffusive adhesion, and mechanical adhesion toat least one element of the light emitting device (such as a carrierfilm with a coating, an optical film, the rear polarizer in an LCD, abrightness enhancing film, another region of the lightguide, a couplinglightguide, a thermal transfer element such as a thin sheet includingaluminum, or a white reflector film). In a further embodiment, at leastone of the core material or cladding material of the lightguide is anadhesive material. In a further embodiment, at least one selected fromthe group: core material, cladding material, and a material disposed ona cladding material of the lightguide is at least one selected from thegroup: a pressure sensitive adhesive, a contact adhesive, a hotadhesive, a drying adhesive, a multi-part reactive adhesive, a one-partreactive adhesive, a natural adhesive, and a synthetic adhesive. In afurther embodiment, the first core material of a first couplinglightguide is adhered to the second core material of a second couplinglightguide due to the adhesion properties of the first core material,second core material, or a combination thereof. In another embodiment,the cladding material of a first coupling lightguide is adhered to thecore material of a second coupling lightguide due to the adhesionproperties of the cladding material. In another embodiment, the firstcladding material of a first coupling lightguide is adhered to thesecond cladding material of a second coupling lightguide due to theadhesion properties of the first cladding material, second claddingmaterial, or a combination thereof. In one embodiment, the core layer isan adhesive and is coated onto at least one selected from the group:cladding layer, removable support layer, protective film, secondadhesive layer, polymer film, metal film, second core layer, low contactarea cover, and planarization layer. In another embodiment, the claddingmaterial or core material has adhesive properties and has an ASTM D3330Peel strength greater than one selected from the group: 8.929, 17.858,35.716, 53.574, 71.432, 89.29, 107.148, 125.006, 142.864, 160.722,178.580 kilograms per meter of bond width when adhered to an element ofthe light emitting device, such as for example without limitation, acladding layer, a core layer, a low contact area cover, a circuit board,or a housing.

In another embodiment, a tie layer, primer, or coating is used topromote adhesion between at least one selected from the group: corematerial and cladding material, lightguide and housing, core materialand element of the light emitting device, cladding material and elementof the light emitting device. In one embodiment, the tie layer orcoating includes a dimethyl silicone or variant thereof and a solvent.In another embodiment, the tie layer includes a phenyl based primer suchas those used to bridge phenylsiloxane-based silicones with substratematerials. In another embodiment, the tie layer includes aplatinum-catalyzed, addition-cure silicone primer such as those used tobond plastic film substrates and silicone pressure sensitive adhesives.

In a further embodiment, at least one region of the core material orcladding material has adhesive properties and is optical coupled to asecond region of the core or cladding material such that the ASTM D1003luminous transmittance through the interface is at least one selectedfrom the group: 1%, 2%, 3%, and 4% greater than the transmission throughthe same two material at the same region with an air gap disposedbetween them.

In one embodiment, the core material of the lightguide includes amaterial with a critical surface tension less than one selected from thegroup: 33, 32, 30, 27, 25, 24 and 20 mN/m. In another embodiment, thecore material has a critical surface tension less than one selected fromthe group: 33, 30, 27, 25, 24 and 20 mN/m and is surface treated toincrease the critical surface tension to greater than one selected fromthe group: 27, 30, 33, 35, 37, 40, and 50. In one embodiment, thesurface treatment includes exposing the surface to at least one selectedfrom the group: a plasma, a flame, and a tie layer material. In oneembodiment, the surface tension of the core material of the lightguideis reduced to reduce light extraction from a surface in contact due to“wet-out” and optical coupling. In another embodiment, the surfacetension of the surface of the lightguide

Multilayer Lightguide

In one embodiment, the lightguide includes at least two layers orcoatings. In another embodiment, the layers or coatings function as atleast one selected from the group: a core layer, a cladding layer, a tielayer (to promote adhesion between two other layers), a layer toincrease flexural strength, a layer to increase the impact strength(such as Izod, Charpy, Gardner, for example), and a carrier layer. In afurther embodiment, at least one layer or coating includes amicrostructure, surface relief pattern, light extraction features,lenses, or other non-flat surface features which redirect a portion ofincident light from within the lightguide to an angle whereupon itescapes the lightguide in the region near the feature. For example, thecarrier film may be a silicone film with embossed light extractionfeatures disposed to receive a thermoset polycarbonate resin core regionincluding a thermoset material

In one embodiment, a thermoset material is coated onto a thermoplasticfilm wherein the thermoset material is the core material and thecladding material is the thermoplastic film or material. In anotherembodiment, a first thermoset material is coated onto a film including asecond thermoset material wherein the first thermoset material is thecore material and the cladding material is the second thermoset plastic.

Environmental Properties

In one embodiment, the light emitting device, display, lightguide,component of the light emitting device, or assembly of components of thelight emitting device (including the adhesives, hardcoating layers,substrates, film-based lightguide, for example) has one or moreenvironmental properties selected from the group: shrinkage orelongation less than 5% at a temperature of 80 degrees Celsius;maintains correct light propagation at air pressures greater than 100pounds per square inch or less than 7 pounds per square inch; and ayellowness index of less than 0.1, 0.3, 0.5, 0.7, or 1 measured usingthe ASTM D1925 standard after exposure to 5-sun UV light (300-400 nm)from a solar simulator at a black panel temperature (BPT) of 44±2degrees Celsius for 100 hours. In one embodiment, the light emittingdevice includes a layer, coating, or material that substantially absorbsUV-A and/or UV-B wavelengths to reduce UV degradation or yellowing ofone or more layers or materials. In another embodiment, the UV absorbingmaterials is physically or optically coupled to (or defined within) acladding layer or material (including an adhesive, for example) on theviewing side of the display.

Light Extraction Method

In one embodiment, one or more of the lightguide, the lightguide region,and the light emitting region includes at least one light extractionfeature or region. In one embodiment, the light extraction region may bea raised or recessed surface pattern or a volumetric region. Raised andrecessed surface patterns include, without limitation, scatteringmaterial, raised lenses, scattering surfaces, pits, grooves, surfacemodulations, microlenses, lenses, diffractive surface features,holographic surface features, photonic bandgap features, wavelengthconversion materials, holes, edges of layers (such as regions where thecladding is removed from covering the core layer), pyramid shapes, prismshapes, and other geometrical shapes with flat surfaces, curvedsurfaces, random surfaces, quasi-random surfaces, and combinationsthereof. The volumetric scattering regions within the light extractionregion may include dispersed phase domains, voids, absence of othermaterials or regions (gaps, holes), air gaps, boundaries between layersand regions, and other refractive index discontinuities orinhomogeneities within the volume of the material different thatco-planar layers with parallel interfacial surfaces.

In one embodiment, the light extraction feature is substantiallydirectional and includes one or more of the following: an angled surfacefeature, a curved surface feature, a rough surface feature, a randomsurface feature, an asymmetric surface feature, a scribed surfacefeature, a cut surface feature, a non-planar surface feature, a stampedsurface feature, a molded surface feature, a compression molded surfacefeature, a thermoformed surface feature, a milled surface feature, anextruded mixture, a blended materials, an alloy of materials, acomposite of symmetric or asymmetrically shaped materials, a laserablated surface feature, an embossed surface feature, a coated surfacefeature, an injection molded surface feature, an extruded surfacefeature, and one of the aforementioned features disposed in the volumeof the lightguide. For example, in one embodiment, the directional lightextraction feature is a 100 micron long, 45 degree angled facet grooveformed by UV cured embossing a coating on the lightguide film thatsubstantially directs a portion of the incident light within thelightguide toward 0 degrees from the surface normal of the lightguide.

In one embodiment, the light extraction feature is a specularly,diffusive, or a combination thereof reflective material. For example,the light extraction feature may be a substantially specularlyreflecting ink disposed at an angle (such as coated onto a groove) orthe light extraction feature may be a substantially diffusely reflectiveink such as an ink including titanium dioxide particles within amethacrylate-based binder. In one embodiment, the thin lightguide filmpermits smaller features to be used for light extraction features orlight extracting surface features to be spaced further apart due to thethinness of the lightguide. In one embodiment, the average largestdimensional size of the light extracting surface features in the planeparallel to the light emitting surface corresponding to a light emittingregion of the light emitting device is less than one selected from thegroup of 3 mm, 2 mm, 1 mm, 0.5 mm, 0.25 mm, 0.1 mm, 0.080, 0.050 mm,0.040 mm, 0.025 mm, and 0.010 mm.

In another embodiment, the fill factor of the light extracting features,light turning features, or low angle directing features defined as thepercentage of the area comprising the features in a square centimeter ina light emitting region, surface or layer of the lightguide or film, isone selected from the group of less than 80%, less than 70%, less than60%, less than 50%, less than 40%, less than 30%, less than 20%, andless than 10%. The fill factor can be measured within a full lightemitting square centimeter surface region or area of the lightguide orfilm (bounded by region is all directions within the plane of thelightguide which emit light) or it may be the average of the lightemitting areas of the lightguides. The fill factor may be measured whenthe light emitting device is in the on state or in the off state (notemitting light) where in the off state, the light extracting featuresare defined as visual discontinuities seen by a person with averagevisual acuity at a distance of less than 10 cm.

The light extraction region may comprise volumetric scattering regionshaving dispersed phase domains, voids, absence of other materials orregions (gaps, holes), air gaps, boundaries between layers and regions,and other refractive index discontinuities within the volume of thematerial different than co-planar layers with parallel interfacialsurfaces. In one embodiment, the light extracting region comprisesangled or curved surface or volumetric light extracting features thatredirect a first redirection percentage of light into an angular rangewithin 5 degrees of the normal to the light emitting surface of thelight emitting device or within 80-90 or 85-90 degrees from thedirection normal to the light emitting surface of the light emittingdevice. In another embodiment, the first redirection percentage isgreater than one selected from the group of 5, 10, 20, 30, 40, 50, 60,70, 80, and 90. In one embodiment, the light extraction features arelight redirecting features, light extracting regions, or light outputcoupling features.

In one embodiment, the lightguide or lightguide region comprises lightextraction features in a plurality of regions. In one embodiment, thelightguide or lightguide region comprises light extraction features onor within at least one selected from the group of one outer surface, twoouter surfaces, two outer and opposite surfaces, an outer surface and atleast one region disposed between the two outer surfaces, within twodifferent volumetric regions substantially within two differentvolumetric planes parallel to at least one outer surface or lightemitting surface or plane, within a plurality of volumetric planes. Inanother embodiment, a light emitting device comprises a light emittingregion on the lightguide region of a lightguide comprising more than oneregion of light extraction features. In another embodiment, one or morelight extraction features are disposed on top of another lightextraction feature. For example, grooved light extraction features couldcomprise light scattering hollow microspheres which may increase theamount of light extracted from the lightguide or which could furtherscatter or redirect the light that is extracted by the grooves. Morethan one type of light extraction feature may be used on the surface,within the volume of a lightguide or lightguide region, or a combinationthereof.

In one embodiment, a first lightguide including a film layer compriseslight extraction features, a second lightguide is defined by a surfaceof a light redirecting optical element and a surface of the firstlightguide, and the light redirecting optical element comprises lightredirecting features or light turning features that are also lightextraction features for the second lightguide.

In a further embodiment, the light extraction features are grooves,indentations, curved, or angled features that redirect a portion oflight incident in a first direction to a second direction within thesame plane through total internal reflection. In another embodiment, thelight extraction features redirect a first portion of light incident ata first angle into a second angle greater than the critical angle in afirst output plane and increase the angular full width at half maximumintensity in a second output plane orthogonal to the first. In a furtherembodiment, the light extraction feature is a region comprising agroove, indentation, curved or angled feature and further comprises asubstantially symmetric or isotropic light scattering region of materialsuch as dispersed voids, beads, microspheres, substantially sphericaldomains, or a collection of randomly shaped domains wherein the averagescattering profile is substantially symmetric or isotropic. In a furtherembodiment, the light extraction feature is a region comprising agroove, indentation, curved or angled feature and further comprises asubstantially anisotropic or asymmetric light scattering region ofmaterial such as dispersed elongated voids, stretched beads,asymmetrically shaped ellipsoidal particles, fibers, or a collection ofshaped domains wherein the average scattering profile is substantiallyasymmetric or an isotropic. In one embodiment, the BidirectionalScattering Distribution Function (BSDF) of the light extraction featureis controlled to create a predetermined light output profile of thelight emitting device or light input profile to a light redirectingelement.

In one embodiment, at least one light extraction feature is an array,pattern or arrangement of a wavelength conversion material selected fromthe group of a fluorophore, phosphor, a fluorescent dye, an inorganicphosphor, photonic bandgap material, a quantum dot material, afluorescent protein, a fusion protein, a fluorophores attached toprotein to specific functional groups, quantum dot fluorophores, smallmolecule fluorophores, aromatic fluorophores, conjugated fluorophores,and a fluorescent dye scintillators, phosphors such as Cadmium sulfide,rare-earth doped phosphor, and other known wavelength conversionmaterials.

In one embodiment, the light extraction feature is a specularly,diffusive, or a combination thereof reflective material. For example,the light extraction feature may be a substantially specularlyreflecting ink disposed at an angle (such as coated onto a groove) or itmay be a substantially diffusely reflective ink such as an inkcomprising titanium dioxide particles within a methacrylate-based binder(white paint). Alternatively, the light extraction feature may be apartially diffusively reflecting ink such as an ink with small silverparticles (micron or sub-micron, spherical or non-spherical, plate-likeshaped or non-plate-like shaped, or silver (or aluminum) coated ontoflakes) further comprising titanium dioxide particles. In anotherembodiment, the degree of diffusive reflection is controlled to optimizeat least one of the angular output of the device, the degree ofcollimation of the light output, and the percentage of light extractedfrom the region.

The pattern or arrangement of light extraction features may vary insize, shape, pitch, location, height, width, depth, shape, orientation,in the x, y, or z directions. Patterns and formulas or equations toassist in the determination of the arrangement to achieve spatialluminance or color uniformity are known in the art of edge-illuminatedbacklights. In one embodiment, a light emitting device comprises afilm-based lightguide comprising light extraction features disposedbeneath lenticules wherein the light extraction features aresubstantially arranged in the form of dashed lines beneath thelenticules such that the light extracted from the line features has alower angular FHWM intensity after redirection from the lenticular lensarray light redirecting element and the length of the dashes varies toassist with the uniformity of light extraction. In another embodiment,the dashed line pattern of the light extraction features varies in the xand y directions (where the z direction is the optical axis of the lightemitting device). Similarly, a two-dimensional microlens array film(close-packed or regular array) or an arrangement of microlenses may beused as a light redirecting element and the light extraction featuresmay comprise a regular, irregular, or other arrangement of circles,ellipsoidal shapes, or other pattern or shape that may vary in size,shape, or position in the x direction, y direction, or a combinationthereof. In one embodiment, at least one of the pitch, first dimensionof the feature in a first direction perpendicular to the thicknessdirection of the film, second dimension of the feature in a seconddirection perpendicular to the first direction and perpendicular to thethickness direction of the film; dimension of the feature in thethickness direction; and density of the features in the first directionand/or second direction varies in the first direction and/or seconddirection. In one embodiment, the non-uniform pitch, feature dimension,or density of the low angle directing features in the first and/orsecond direction is used to direct light to an angle less than thecritical angle for one or more interfaces of the core region of thelightguide with a spatially uniform luminous flux such that the lightcoupling through the cladding layer or region with the higher refractiveindex than the cladding layer or region on the opposite surface of thecore region of the lightguide is incident on one or more light turningfeatures that direct the light to an angular range within thirty degreesfrom the thickness direction of the lightguide in the light emittingregion. In one embodiment, varying the pitch, feature dimension, ordensity of the low angle directing features in the first and/or seconddirection enables spatial control of the light flux redirected towardthe light turning features wherein the low angle directing features donot cause moiré interference with the object being illuminated by thelight emitting device (such as a reflective or transmissive liquidcrystal display). Thus, in this example, the pitch of the light turningfeatures can be chosen to be a constant pitch that does not create moiréinterference and the luminance uniformity of the light reaching theobject of illumination is achieved by spatially varying the pitch,feature dimension, or density of the low angle directing features. Inone embodiment, a method of providing uniform illuminance for an objectincludes providing a plurality of types of light directing features(such as low angle directing features and light turning features)wherein the uniformity is provided by varying the pitch, dimension, ordensity of a first type of feature and the redirection of light to anangle that escapes the lightguide to illuminate an object (such as areflective or transmissive LCD) is achieved by a second type of featurewith a substantially constant pitch, dimension, and/or density such thatthe moiré contrast between the light directing features and the objectof illumination is less than one selected from the group of 50%, 40%,30%, 20% and 10%. The low angle directing feature may be formed on asurface or within a volume of material and the material may bethermoplastic, thermoset, or adhesive material. In one embodiment, thelow angle directing features are light extraction features. In anotherembodiment, the low angle directing features are light extractionfeatures for a first lightguide and a second lightguide. In anotherembodiment, the light emitting device comprises low angle directingfeatures in two or more layers or regions in the direction of the lightoutput of the light emitting device.

Low Angle Directing Features

In one embodiment, at least one of the coupling lightguides, lightmixing region, or light emitting region comprises two or more low angledirecting features. As used herein, low angle directing features arerefractive, total internal reflection, diffractive, or scatteringsurfaces, features, or interfaces that redirect light propagating withina totally internally reflecting lightguide at a first angle to thethickness direction of the film in the core region of the lightguide toa second angle in the core region of the lightguide smaller than thefirst angle by an average total angle of deviation of less than 20degrees. In another embodiment, the low angle directing featuresredirect incident light to a second angle with an average total angle ofdeviation less than one selected from the group 18, 16, 14, 12, 10, 8,6, 5, 4, 3, 2, and 1 degrees from the angle of incidence. In oneembodiment, the low angle directing features are defined by one or morereflective surfaces of the reflective spatial light modulator. Forexample, in one embodiment, the rear reflective surface of a reflectivespatial light modulator comprises low angle directing features and thereflective spatial light modulator is optically coupled to thelightguide in the light emitting region. In another example, thereflective pixels of a reflective spatial light modulator are low angledirecting features and the reflective spatial light modulator isoptically coupled to the lightguide in the light emitting region.

In one embodiment, at least one of the pitch, first dimension of thefeature in a first direction perpendicular to the thickness direction ofthe film, second dimension of the feature in a second directionperpendicular to the first direction and perpendicular to the thicknessdirection of the film; dimension of the feature in the thicknessdirection; and density of the features in the first direction and/orsecond direction varies in the first direction and/or second direction.In one embodiment, the non-uniform pitch, feature dimension, or densityis used to direct light to an angle less than the critical angle for oneor more interfaces of the core region of the lightguide with a spatiallyuniform luminous flux such that the light coupling through the claddinglayer or region with the higher refractive index than the cladding layeror region on the opposite surface of the core region of the lightguideis incident on one or more light turning features that direct the lightto an angular range within thirty degrees from the thickness directionof the lightguide in the light emitting region. In one embodiment,varying the pitch, feature dimension, or density of the low angledirecting features in the first and/or second direction enables spatialcontrol of the light flux redirected toward the light turning featureswherein the low angle directing features do not cause moiré interferencewith the object being illuminated by the light emitting device (such asa reflective or transmissive liquid crystal display). Thus, in thisexample, the pitch of the light turning features can be chosen to be aconstant pitch that does not create moiré interference and the luminanceuniformity of the light reaching the object of illumination is achievedby spatially varying the pitch, feature dimension, or density of the lowangle directing features. In one embodiment, a method of providinguniform illuminance for an object includes providing a plurality oftypes of light directing features (such as low angle directing featuresand light turning features) wherein the uniformity is provided byvarying the pitch, dimension, or density of a first type of feature andthe redirection of light to an angle that escapes the lightguide toilluminate an object (such as a reflective or transmissive LCD) isachieved by a second type of feature with a substantially constantpitch, dimension, and/or density such that the moiré contrast betweenthe light directing features and the object of illumination is less thanone selected from the group of 50%, 40%, 30%, 20% and 10%. The low angledirecting feature may be formed on a surface or within a volume ofmaterial and the material may be thermoplastic, thermoset, or adhesivematerial. In one embodiment, the low angle directing features are lightextraction features. In a further embodiment, the light redirectingfeatures are low angle directing features. In another embodiment, thelow angle directing features are light extraction features for a firstlightguide and a second lightguide. In another embodiment, the lightemitting device comprises low angle directing features in two or morelayers or regions in the direction of the light output of the lightemitting device.

In one embodiment, the light redirecting element has a refractive indexless than or equal to the refractive index of the core layer of thefilm-based lightguide. For example, in one embodiment a reflectivedisplay comprises a frontlight having a light redirecting element formedin a polycarbonate material with a refractive index of about 1.6 that isoptically coupled to a polycarbonate lightguide with a refractive indexof about 1.6 using an adhesive functioning as a cladding layer with arefractive index of about 1.5 where the lightguide comprises low angledirecting features that are light extracting features for the film-basedlightguide and the lightguide is optically coupled to a reflectivespatial light modulator on a side opposite the light redirecting opticalelement using an adhesive that functions as a cladding with a refractiveindex of about 1.42.

In one embodiment, a light emitting device comprises a film-basedlightguide comprising a core layer having opposing surfaces with athickness not greater than about 0.5 millimeters therebetween whereinlight propagates by total internal reflection between the opposingsurfaces; a first cladding layer having a first side optically coupledto the core layer and an opposing second side; an array of couplinglightguides continuous with a lightguide region of the lightguide, eachcoupling lightguide of the array of coupling lightguides terminates in abounding edge, and each coupling lightguide is folded in a fold regionsuch that the bounding edges of the array of coupling lightguides arestacked; a light emitting region comprising a plurality of lightextraction features arranged in a pattern that varies spatially in thelight emitting region, the plurality of light extraction featuresfrustrate totally internally reflected light propagating within the corelayer such that light exits the core layer in the light emitting regioninto the first cladding layer; a light source positioned to emit lightinto the stacked bounding edges, the light propagating within the arrayof coupling lightguides to the lightguide region, with light from eachcoupling lightguide combining and totally internally reflecting withinthe lightguide region; a light redirecting optical element opticallycoupled to the second side of the first cladding layer, the lightredirecting optical element comprising light redirecting features thatdirect frustrated totally internally reflected light from the lightextraction features toward the reflective spatial light modulator, thelight redirecting features occupy less than 50% of a surface of thelight redirecting optical element in the light emitting region, andwherein the core layer has an average thickness in the light emittingregion, the light emitting region has a largest dimension in a plane ofthe light emitting region orthogonal to the thickness direction of thecore layer, the largest dimension of the light emitting region dividedby the average thickness of the core layer in the light emitting regionis greater than 100, the light extraction features are low angledirecting features, the light exiting the light source has a first fullangular width at half maximum intensity in a plane orthogonal to thethickness direction of the film, the light exiting the light emittingdevice has second full angular width at half maximum intensity in asecond plane parallel to the thickness direction and a third fullangular width at half maximum intensity in a third plane parallel to thethickness direction of the film and orthogonal to the second plane. Inone embodiment, the first full angular width is less than one selectedfrom the group: 1, 2, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, and 50degrees. In another embodiment, the second full angular width is lessthan one selected from the group: 1, 2, 5, 7, 10, 15, 20, 25, 30, 35,40, 45, and 50 degrees. In another embodiment, the third full angularwidth is less than one selected from the group: 1, 2, 5, 7, 10, 15, 20,25, 30, 35, 40, 45, and 50 degrees. In another embodiment, the first,second, and third full angular widths are each less than one selectedfrom the group 1, 2, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, and 50degrees. In one embodiment, the light exiting the light source has afull angular width at half maximum intensity in a plane parallel to thethickness direction of the film greater than the first full angularwidth. For example, in one embodiment, a light source is substantiallycollimated in a plane perpendicular to the thickness direction of thelightguide, film, or stack of coupling lightguides, in the lightemitting region (or has a first angular width at half maximum intensityless than 10 degrees) and is not collimated or has a larger full angularwidth at half maximum intensity in the plane parallel to the thicknessdirection of the film or stack of coupling lightguides. In oneembodiment, light from the light sources passes through the couplinglightguides and into the lightguide region, it is redirected by the lowangle directing features, passes through the first cladding layer, isredirected by the light redirecting optical element and exits the lightemitting device with second angular full width at half maximum intensitythat can be low (such as less than 10 degrees) due to the collimation ofthe light source output (such as by a primary and/or secondary lens orreflector) and a third angular full width at half maximum intensity thatcan be low (such as less than 10 degrees) due to the collimation fromthe combination of the low angle directing features, the difference inrefractive index between the two cladding layers, and the lightredirecting features of the light redirecting optical element.

Reflecting Low Angle Directing Features

In one embodiment, a film-based lightguide comprises a light emittingregion with low angle directing features defined by angled or curvedinterfaces between materials with two different refractive indexes. Inthis embodiment, the refractive index difference can cause at least aportion of the incident light to be reflected with an average totalangle of deviation less than 20 degrees from the angle of incidence. Inone embodiment, light propagating within a core region of a lightguideof a first core material with a first core refractive index adjacent aregion with a second refractive index less than the first refractiveindex interacts and reflects from angled surface features embossed intothe first core material such that at least a portion of the incidentlight is reflected with an average total angle of deviation less than 20degrees from the angle of incidence. In one embodiment, the reflectionat the angled or curved surface feature is a total internal reflection.For example, in one embodiment, a film-based lightguide comprises alight emitting region with low angle directing features defined by anarrangement of linear surface features angled at an average of 4 degreesfrom the direction parallel to the film surface (or core region layerinterface) in the light emitting region (an average of 86 degrees fromthe surface normal of the film in the light emitting region). In thisexample, the surfaces can be formed (such as by scribing or embossing)in the core layer of material and a material with a lower refractiveindex may be positioned adjacent the surface such that a portion of thelight incident on the surface is reflected (low angle directed) at atotal angle of deviation of 8 degrees.

Refractive Low Angle Directing Features

In another example, a film-based lightguide comprises a light emittingregion with low angle directing features defined by an arrangement ofsurfaces wherein light passing through the surface is refracted (andoptionally reflected) at least once to a new angle with an average totalangle of deviation less than 20 degrees from the angle of incidence. Inthis example, the surfaces can be formed in the core layer of materialand have a material with a lower refractive index adjacent the surfacesuch that a portion of the light incident on the surface is refracted(low angle directed) at the interface, passes through the lowerrefractive index material and reflects off a second interface, passesback through the lower refractive index material and back through thelightguide where it may escape the lightguide at the opposite surfaceinterface and be subsequently redirected by light turning features.

Diffracting Low Angle Directing Features

In another example, a film-based lightguide comprises a light emittingregion with low angle directing features defined by an arrangement ofdiffractive features or surfaces wherein light passing through thefeatures or surfaces is diffracted (and optionally reflected) at leastonce to a new angle with an average total angle of deviation less than20 degrees from the angle of incidence. For example, in one embodiment,one surface of the film-based lightguide in the light emitting region ofthe film comprises binary gratings or blazed diffraction gratings thatredirect light incident at a first angle within a first wavelengthbandwidth to a second angle different from the first angle with anaverage total angle deviation less than 20 degrees from the angle ofincidence. In one embodiment, the pitch, size, length size, depth, orangle of the one or more diffractive features or surfaces varies in afirst direction from the first side of the light emitting region to theopposite side in the direction of light propagation within the lightemitting region. For example, in one embodiment, the core region of thelightguide in the light emitting region comprises diffraction gratingswith a repeating array of first, second, and third pitches configured todiffract the average angle of incident light into average total angledeviations less than 20 degrees for blue, green, and red light,respectively.

Scattering Low Angle Directing Features

In a further example, a film-based lightguide comprises a light emittingregion with low angle directing features defined by a layer or regionwith light scattering features, domains, or particles wherein lightpassing through the light scattering layer or region is scattered atleast once to a new angle with an average total angle of deviation lessthan 20, 15, 10, 8, 6, 4, 3, 2, or 1 degrees from the angle ofincidence. In one embodiment, the light scattering layer or region canbe formed adjacent, above, below, or within a region of the core layerof material. In this example, the light scattering layer or region maycomprise or be defined by a light scattering interface with a regular orirregular surface structure on a first material with a first refractiveindex in contact with a second surface of a second material conformingto the first material surface with a lower or higher refractive indexthan the first material such that a portion of the light incident on theinterface is scattered (forward and/or back scattering) such that itescapes the lightguide at a surface interface and is subsequentlyredirected by light turning features. In another embodiment, thefilm-based lightguide comprises low angle scattering features defined bya dispersed phase of a first material in a second matrix material (suchas dispersed beads within a coating matrix). In this embodiment, thelight incident scatters or refracts from one or more domain-matrixinterfaces such that the average total angle of deviation of theincident light is less than 20 degrees from the angle of incidence. Inone embodiment, the low angle directing features progressively redirectlight such that the light is deviated into an angle such that all or aportion of the light escapes the total internal reflection conditionwithin the lightguide.

Polarization Dependent Low Angle Directing Features

In one embodiment, the low angle directing features redirect light witha first polarization more than light with a second polarizationdifferent than the first polarization. In another embodiment, the ratioof the percentage of the light with the first polarization that isredirected to the percentage of light with the second polarization thatis redirected, the polarization directing ratio, is greater than oneselected from the group: 1, 2, 3, 4, 5, 10, 15, 20, 30, and 50. Forexample, in one embodiment, the first polarization is s-polarized lightand the second polarization is p-polarized light. In one embodiment, thelow angle directing features or surface or a material optically coupledto the low angle directing features or surface comprise a substantiallyisotropic material, a birefringent material, or a trirefringentmaterial. In one embodiment, a structured low angle directing feature ina birefringent material is used to redirect light of a firstpolarization such that the average total angle of deviation of theincident light is less than 20 degrees from the angle of incidence. Forexample, in one embodiment, light of the first polarization, such ass-polarized light, is directed into a low angle such that it is at anangle less than the critical angle for the side of the lightguideoptically coupled to the cladding layer with a higher refractive indexthan the cladding layer on the opposite side. Thus, in this example,light of the desired polarization state, s-polarized light, ispreferentially extracted by the low angle directing features. In anotherembodiment, one or more layers or regions optically coupled to thelightguide comprises a waveplate, birefringent material, trirefringentmaterial, or anisotropic material that converts light remaining in thelightguide into the desired polarization state such that it can beredirected through a second or subsequent interaction with thepolarization dependent low angle directing feature.

Light Turning Features

In one embodiment, the light emitting region of the lightguide comprisesor is optically coupled to a layer or region with light turningfeatures. As used herein, light turning features are refractive, totalinternal reflection, diffractive, or scattering surfaces, features, orinterfaces that redirect at least a portion of light incident within afirst angular range to a second angular range different from the first,wherein the second angular range is within 30 degrees from the thicknessdirection of the film in the light emitting region. For example in oneembodiment, a polycarbonate film with grooves on a first outer surfaceis optically coupled to a film-based lightguide using a pressuresensitive adhesive on the second surface of the polycarbonate filmopposite the first outer surface. In this embodiment, light escaping thelightguide (such as by low angle directing features) through thepressure sensitive adhesive totally internally reflects at thegroove-air interface in the polycarbonate film and is directed to anangle within 30 degrees from the thickness direction of the film in thelight emitting region where it further passes through the lightguide toilluminate an object, such as a reflective LCD, and may optionally passback through the lightguide. In one embodiment, the light turningfeatures receive light from the low angle directing features andredirect the light into an angle less than 30 degrees from the thicknessdirection in the light emitting region. The light turning feature may beformed on a surface or within a volume of material and the material maybe thermoplastic, thermoset, or adhesive material. In one embodiment,the light turning features are embossed (UV cured or thermomechanicallyembossed) surface features in a light turning film that is opticallycoupled (such as by using a pressure sensitive adhesive) to thefilm-based lightguide in the light emitting region. In one embodiment, alight turning film comprising light turning features on a first surfaceof the film is optically coupled to the lightguide on the second surfaceopposite the first surface, the light turning features comprise recessedregions or grooves in the first surface, and the first surface isadhered to a second film in regions between the recessed regions orgrooves using a pressure sensitive adhesive that leaves an air gap inthe recessed region or grooves. In this embodiment, the large refractiveindex difference between the polymer light turning film and the airwithin the recessed region or grooves increases the percentage oftotally internally reflected light at the interface over that of anadhesive that effectively planarizes the surface by filing in therecessed regions or grooves with the adhesive. In another embodiment,the light turning film or region or layer comprising the light turningfeatures extends into less than one selected from the group of 30%, 20%,10%, and 5% of the light mixing region of the film-based lightguide.

Size and Shape of the Light Turning Features

In one embodiment, a light emitting device comprises the film-basedlightguide providing front illumination, such as a frontlight for areflective display, and the density of the light turning features in thelight emitting region of the film (or in a film optically coupled to thelight emitting region) is less than about 50% in order to reduceundesired second light deviations (such as unwanted reflections) of thelight reflected from the object illuminated and passing back through thelightguide and layer or region comprising the light turning features. Inone embodiment, the area density or density along a first direction ofthe light turning features in the light emitting region of thelightguide is a first density selected from the group: less than 50%;less than 40%; less than 30%; between 1% and 50%; between 1% and 40%;between 1% and 30%; between 5% and 30%; and between 5% and 20%. Inanother embodiment, the density and/or dimension of the light turningfeatures in the first and/or second direction is less than the firstdensity and the light turning features are not visible from distance of18 inches or more by a person with a visual acuity of 1 arcminute. Inanother embodiment, the angle subtended by the dimension of the lightturning features in the first direction and/or second direction is lessthan one arcminute at a distance of 18 inches. In a further embodiment,area density in a plane comprising the first direction and the seconddirection of the light turning features is less than the first densityand the light turning features redirect less than one selected from thegroup: 50%, 40%, 30%, 20%, and 10% of the light reflected from theobject of illumination (such as a reflective display) back toward theobject of illumination. Thus, in this embodiment, the density and/ordimensions of the light turning features can be configured to reduce thelight reflected back toward the object which could reduce the visibleluminance contrast of the object.

In another embodiment, the average depth of the light turning featuresin the thickness direction of the layer or region of film comprising thelight turning features is one or more selected from the group: between 1and 500 microns, between 3 and 300 microns, between 5 and 200 microns,greater than 2 microns, less than 500 microns, less than 200 microns,less than 100 microns, less than 75 microns, less than 50 microns, andless than 10 microns.

In another embodiment, the average width of the light turning featuresin the direction of light propagation from a first input side of thelight emitting region of the lightguide to the opposite side of thelight emitting region of the lightguide is one or more selected from thegroup: between 2 and 500 microns, between 5 and 300 microns, between 10and 200 microns, greater than 5 microns, less than 500 microns, lessthan 200 microns, less than 100 microns, less than 75 microns, less than50 microns, less than 25 microns, and less than 10 microns.

In one embodiment, the light turning feature includes one or more of thefollowing: an angled surface feature, a curved surface feature, a roughsurface feature, a random surface feature, an asymmetric surfacefeature, a scribed surface feature, a cut surface feature, a non-planarsurface feature, a stamped surface feature, a molded surface feature, acompression molded surface feature, a thermoformed surface feature, amilled surface feature, a composite of symmetric or asymmetricallyshaped materials, a laser ablated surface feature, an embossed surfacefeature, a coated surface feature, an injection molded surface feature,an extruded surface feature, and one of the aforementioned featurespositioned in the volume of the lightguide.

In one embodiment, a reflective display comprises a light emittingdevice with a film-based lightguide and a reflective spatial lightmodulator. In this embodiment, the light emitting device comprises alight redirecting optical element with light redirecting features orlight turning features with a dimension in a plane orthogonal to thethickness direction of the film-based lightguide larger than the averagesize of a pixel of the reflective spatial light modulator or larger thanthe size of 2, 3, 4, 5, 7, 10, 20, 30, or 50 average size pixels.

In another embodiment, the ratio of the average spacing between lightredirecting features or light turning features to the average dimensionof the light redirecting features or light turning features in adirection in a plane orthogonal to the thickness direction of thefilm-based lightguide is greater than one selected from the group 1,1.5, 2, 3, 4, 5, 7, 10, 15, 20, 30, 40, 50, 70, and 100.

Pitch of the Light Turning Features

In one embodiment the average pitch or spacing between the lightredirecting features or light turning features is constant. In oneembodiment, the average pitch of the light turning features in thedirection of light propagation from a first input side of the lightemitting region of the lightguide to the opposite side of the lightemitting region of the lightguide (such as the direction of the averageangle of propagation within the lightguide in the light emitting region,for example) is one or more selected from the group: between 5 and 500microns, between 10 and 300 microns, between 20 and 200 microns, greaterthan 5 microns, less than 500 microns, less than 200 microns, less than100 microns, less than 75 microns, and less than 50 microns. In oneembodiment, the pitch of the light turning features is substantiallyconstant. In one embodiment, the pitch of the light turning features orlight redirecting features is configured to reduce moiré contrast withregularly spaced elements of the object of illumination, such as areflective or transmissive LCD.

The visibility of the moiré interference pattern can be visuallydistracting in a light emitting device such as a display and reduces theluminance uniformity. The visibility, or luminance contrast of the moirépatterns is defined as LMmax−LMmin/(LMmax+LMmin) where LMmax and LMminare the maximum and minimum luminance, respectively, along a crosssection substantially perpendicular to the repeating moiré pattern whenthe elements are illuminated. In one embodiment, the moiré contrast ofthe light emitting device comprising the light turning features or lightredirecting features, is low such that the moiré contrast is less thanone selected from the group of 50%, 40%, 30%, 20% and 10%. The moirécontrast may be reduced by shifting the pitch of the light turningfeatures or light redirecting features relative to the regular featuresof the object of illumination such that the moiré contrast issufficiently small enough not to be visible to the naked eye or be seenwithout close inspection. The moiré contrast can be reduced oressentially eliminated by one or more of the following methods:adjusting the pitch of the light turning features or light redirectingfeatures, rotating the light turning features or light redirectingfeatures relative to the regular array of features in the object ofillumination, randomizing the pitch of the light turning features orlight redirecting features, or increasing the spacing between the lightturning features or light redirecting features and the object ofillumination.

In another embodiment, the light redirecting features or light turningfeatures are spaced at a first distance from the pixels of a spatiallight modulator, where the first distance is greater than one selectedfrom the group: 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1,1.5, and 2 millimeters. In another embodiment, a light emitting devicecomprises a lens positioned to receive light redirected by the lightredirecting features or light turning features that reflects ortransmits through a spatial light modulator, wherein the modulationtransfer function for the lens at the first distance or location of thelight turning features or light redirecting features is less than 0.5and modulation transfer function for the lens is greater than 0.7 at aplane comprising the pixels of the spatial light modulator. For example,in one embodiment, a head-mounted display comprises a film-basedlightguide, a light redirecting element, a reflective spatial lightmodulator, and a lens (or combination of lenses) to magnify the pixelsof the reflective spatial light modulator wherein the light redirectingfeatures of the light redirecting element are positioned at a firstdistance from the pixels of the reflective spatial light modulator suchthat the modulation transfer function for the light redirecting featuresis less than 0.5 and the light redirecting features are not discernableor barely discernable for a person with an average acuity of 1arcminute. Similarly, in a projection system, the modulation transferfunction of a lens for the location of the light turning features orlight redirecting features may be less than 0.5.

By adjusting the pitch of the light turning features when they aresubstantially parallel to the features in the object of illumination,the moiré contrast can be reduced. In one embodiment, the ratio of thepitches between the array of light turning features and the pitch of theregular features in the object of illumination (such as pixels in adisplay) is equal to 1/(N+0.5) where N is an integer and the moirécontrast is reduced or eliminated. A pitch ratio from 0.9/(N+0.5) to1.1/(N+0.5) will have a relatively low visibility of moiré. In oneembodiment, the pitch of the light turning features and the pitch of theregular array of elements on the object of illumination (such a regulararray of pixels in a reflective LCD) is in accordance with the aboveequation and has an acceptable level of moiré visibility. In oneembodiment, a light emitting device comprises light turning featureswith a first pitch P1, the light turning features positioned to redirectlight to an angle within 30 degrees from the thickness direction of thefilm toward an object of illumination with a regular array of elements(such as pixels in a reflective LCD) with a second pitch P2 wherein0.9/(N+0.5)<P2/P1<1.1/(N+0.5) where N is an integer.

Polarization Dependent Light Turning Features

In one embodiment, the light turning features redirect light with afirst polarization more than light with a second polarization differentthan the first polarization. In another embodiment, the ratio of thepercentage of the light with the first polarization that is redirectedto the percentage of light with the second polarization that isredirected, the polarization directing ratio, is greater than oneselected from the group: 1, 2, 3, 4, 5, 10, 15, 20, 30, and 50. Forexample, in one embodiment, the first polarization is s-polarized lightand the second polarization is p-polarized light. In one embodiment, thelight turning features or surface or a material optically coupled to thelight turning features or surface comprise a substantially isotropicmaterial, a birefringent material, or a trirefringent material. In oneembodiment, a structured light turning feature in a birefringentmaterial is used to redirect light of a first polarization such that theaverage total angle of deviation of the incident light is less than 20degrees from the angle of incidence. For example, in one embodiment,light from low angle directing features incident on the light turningfeature of the first polarization, such as s-polarized light, isdirected into an angle from the thickness direction of the film in thelight emitting region less than 30 degrees such that it escapes thefilm-based lightguide in the light emitting region, such as toilluminate a reflective display, and may optionally pass back throughthe lightguide. Light of the second polarization may pass through thelight turning feature and totally internally reflect at an interfacefurther from the core region of the lightguide. In this example, thelight of the second polarization may be changed to the firstpolarization state and be recycled within the lightguide and layersoptically coupled to the lightguide. Thus, in this example, light of thedesired polarization state, s-polarized light for example, ispreferentially directed to an angle such that it can transmit out of thelightguide and layers by the light turning features. The light turningfeatures may directly couple light out of the lightguide without passingback through the core region of the lightguide or the light turningfeatures may direct the light to the opposite side of the lightguidetoward an object for front illumination. In another embodiment, one ormore layers or region optically coupled to the lightguide comprises awaveplate, birefringent, trirefringent, or anisotropic material thatconverts light remaining in the lightguide into the desired polarizationstate such that it can be redirected through a second or subsequentinteraction with the polarization dependent light turning feature.

Multiple Lightguides

In one embodiment, a light emitting device includes more than onelightguide to provide one or more of the following: color sequentialdisplay, localized dimming backlight, red, green, and blue lightguides,animation effects, multiple messages of different colors, NVIS anddaylight mode backlight (one lightguide for NVIS, one lightguide fordaylight for example), tiled lightguides or backlights, and large arealight emitting devices including smaller light emitting devices. Inanother embodiment, a light emitting device includes a plurality oflightguides optically coupled to each other. In another embodiment, atleast one lightguide or a component thereof includes a region withanti-blocking features such that the lightguides do not substantiallycouple light directly into each other due to touching.

Multiple Lightguides to Provide Pixelated Color

In one embodiment, a light emitting device includes a first lightguideand second lightguide disposed to receive light from a first and secondlight source, respectively, through two different optical paths whereinthe first and second light source emit light of different colors and thelight emitting regions of the first and second lightguides includepixelated regions spatially separated in the plane including the lightoutput plane of the light emitting device at the pixelated regions (forexample, separated in the thickness direction of the film-basedlightguides). In one embodiment, the colors of the first and secondpixelated light emitting regions are perceived by a viewer with a visualacuity of 1 arcminute without magnification at a distance of two timesthe diagonal (or diameter) of the light emitting region to be theadditive color of the combination of sub-pixels. For example, in oneembodiment, the color in different spatial regions of the display isspatially controlled to achieve different colors in different regions,similar to liquid crystal displays using red, green, and blue pixels andLED signs using red green and blue LEDs grouped together. For example,in one embodiment, a light emitting device includes a red light emittinglightguide optically coupled to a green light emitting lightguide thatis optically coupled to a blue lightguide. Various regions of thelightguides and the light output of this embodiment are describedhereafter. In a first light emitting region of the light emittingdevice, the blue and green lightguides have no light extraction featuresand the red lightguide has light extraction features such that the firstlight emitting region emits red in one or more directions (for example,emitting red light toward a spatial light modulator or out of the lightemitting device). In a second light emitting region of the lightemitting device, the red and green lightguides have no light extractionfeatures and the blue lightguide has light extraction features such thatthe second light emitting region emits blue light in one or moredirections. In a third light emitting region of the light emittingdevice, the blue and red lightguides have light extraction features andthe green lightguide does not have any light extraction features suchthat the third light emitting region emits purple light in one or moredirections. In a fourth light emitting region of the light emittingdevice, the blue, green, and red lightguides have light extractionfeatures such that the fourth light emitting region emits white light inone or more directions. Thus, by using multiple lightguides to createlight emitting regions emitting light in different colors, the lightemitting device, display, or sign, for example, can be multi-coloredwith different regions emitting different colors simultaneously orsequentially. In another embodiment, the light emitting regions includelight extraction features of appropriate size and density on a pluralityof lightguides such that a full-color graphic, image, indicia, logo orphotograph, for example, is reproduced.

Lightguide Folding Around Components

In one embodiment, at least one selected from the group: lightguide,lightguide region, light mixing region, plurality of lightguides,coupling lightguides, and light input coupler bends or folds such thatthe component other components of the light emitting device are hiddenfrom view, located behind another component or the light emittingregion, or are partially or fully enclosed. These components aroundwhich they may bend or fold include components of the light emittingdevice such as light source, electronics, driver, circuit board, thermaltransfer element, spatial light modulator, display, housing, holder, orother components such that the components are disposed behind the foldedor bent lightguide or other region or component. In one embodiment, afrontlight for a reflective display includes a lightguide, couplinglightguides and a light source wherein one or more regions of thelightguide are folded and the light source is disposed substantiallybehind the display. In one embodiment, the light mixing region includesa fold and the light source and/or coupling lightguides aresubstantially disposed on the side of the film-based lightguide oppositethe light emitting region of the device or reflective display. In oneembodiment, a reflective display includes a lightguide that is foldedsuch that a region of the lightguide is disposed behind the reflectivespatial light modulator of the reflective display. In one embodiment,the fold angle is between 150 and 210 degrees in one plane. In anotherembodiment, the fold angle is substantially 180 degrees in one plane. Inone embodiment, the fold is substantially 150 and 210 degrees in a planeparallel to the optical axis of the light propagating in the film-basedlightguide. In one embodiment, more than one input coupler or componentis folded behind or around the lightguide, light mixing region or lightemitting region. In this embodiment, for example, two light inputcouplers from opposite sides of the light emitting region of the samefilm may be disposed adjacent each other or utilize a common lightsource and be folded behind the spatial light modulator of a display. Inanother embodiment, tiled light emitting devices include light inputcouplers folded behind and adjacent or physically coupled to each otherusing the same or different light sources. In one embodiment, the lightsource or light emitting area of the light source is disposed within thevolume bounded by the edge of the light emitting region and the normalto the light emitting region on the side of the lightguide opposite theviewing side. In another embodiment, at least one of the light source,light input coupler, coupling lightguides, or region of the light mixingregion is disposed behind the light emitting region (on the side of thelightguide opposite the viewing side) or within the volume bounded bythe edge of the light emitting region and the normal to the lightemitting region on the side of the lightguide opposite the viewing side.

In another embodiment, the lightguide region, light mixing region, orbody of the lightguide extends across at least a portion of the array ofcoupling lightguides or a light emitting device component. In anotherembodiment, the lightguide region, light mixing region, or body of thelightguide extends across a first side of the array of couplinglightguides or a first side of the light emitting device component. In afurther embodiment, the lightguide region, light mixing region or bodyof the lightguide extends across a first side and a second side of thearray of coupling lightguides. For example, in one embodiment, the bodyof a film-based lightguide extends across two sides of a stack ofcoupling lightguides with a substantially rectangular cross section. Inone embodiment, the stacked array of coupling lightguides is oriented ina first orientation direction substantially parallel to their stackedsurfaces toward the direction of light propagation within the couplinglightguides, and the light emitting region is oriented in a seconddirection parallel to the optical axis of light propagating within thelight emitting region where the orientation difference angle is theangular difference between the first orientation direction and thesecond orientation direction. In one embodiment, the orientationdifference angle is selected from the group: 0 degrees, greater than 0degrees, greater than 0 degrees and less than 90 degrees, between 70degrees and 110 degrees, between 80 degrees and 100 degrees, greaterthan 0 degrees and less than 180 degrees, between 160 degrees and 200degrees, between 170 degrees and 190 degrees, and greater than 0 degreesand less than 360 degrees.

In one embodiment, at least one selected from the group: lightguide,lightguide region, light mixing region, plurality of lightguides,coupling lightguides, and light input coupler bends or folds such thatit wraps around a component of the light emitting device more than once.For example, in one embodiment, a lightguide wraps around the couplinglightguides two times, three times, four times, five times, or more thanfive times. In another embodiment, the lightguide, lightguide region,light mixing region, plurality of lightguides, coupling lightguides, orlight input coupler may bend or fold such that it wraps completelyaround a component of the light emitting device and partially wrapsagain around. For example, a lightguide may wrap around a relativeposition maintaining element 1.5 times (one time around and half wayaround again). In another embodiment, the lightguide region, lightmixing region or body of the lightguide further extends across a third,fourth, fifth, or sixth side of the array of coupling lightguides orlight emitting device component. For example, in one embodiment, thelight mixing region of a film-based lightguide extends completely aroundfour sides of the relative position maintaining element plus across aside again (fifth side). In another example, the light mixing regionwraps around a stack of coupling lightguides and relative positionmaintaining element more than three times.

In one embodiment, wrapping the lightguide, lightguide region, lightmixing region, plurality of lightguides, coupling lightguides, or lightinput coupler around a component provides a compact method for extendingthe length of a region of the lightguide. For example, in oneembodiment, the light mixing region is wrapped around the stack ofcoupling lightguides to increase the light mixing distance within thelight mixing region such that the spatial color or the light fluxuniformity of the light entering the light emitting region is improved.

In one embodiment, the wrapped or extended region of the lightguide isoperatively coupled to the stack of coupling lightguides or a componentof the light emitting device. In one embodiment, the wrapped or extendedregion of the lightguide is held with adhesive to the stack of couplinglightguides or the component of the light emitting device. For example,in one embodiment, the light mixing region includes a pressure sensitiveadhesive cladding layer that extends or wraps and adheres to one or moresurfaces of one or more coupling lightguides or to the component of thelight emitting device. In another embodiment, the light mixing regionincludes a pressure sensitive adhesive layer that adheres to at leastone surface of a relative position maintaining element. In anotherembodiment, a portion of the film-based lightguide includes a layer thatextends or wraps to one or more surfaces of one or more couplinglightguides or a component of the light emitting device. In anotherembodiment, the wrapped or extended region of the lightguide extendsacross one or more surfaces or sides, or wraps around one or more lightsources. The wrapping or extending of a lightguide or lightguide regionacross one or more sides or surfaces of the stack of couplinglightguides or the component of the light emitting device, may occur byphysically translating or rotating the lightguide or the lightguideregion, or may occur by rotating the stack of coupling lightguides orthe component. Thus, the physical configuration does not require aparticular method of achieving the wrapping or extending.

Light Absorbing Region or Layer

In one embodiment, one or more of the cladding, the adhesive, the layerdisposed between the lightguide and lightguide region and the outerlight emitting surface of the light emitting device, a patterned region,a printed region, and an extruded region on one or more surfaces orwithin a volume of the film includes a light absorbing material whichabsorbs a first portion of light in a first predetermined wavelengthrange.

Adhesion Properties of the Lightguide, Film, Cladding or Other Layer

In one embodiment, one or more of the lightguide, the core material, thelight transmitting film, the cladding material, and a layer disposed incontact with a layer of the film has adhesive properties or includes amaterial with one or more of the following: chemical adhesion,dispersive adhesion, electrostatic adhesion, diffusive adhesion, andmechanical adhesion to at least one element of the light emitting device(such as a carrier film with a coating, an optical film, the rearpolarizer in an LCD, a brightness enhancing film, another region of thelightguide, a coupling lightguide, a thermal transfer element such as athin sheet including aluminum, or a white reflector film) or an elementexternal to the light emitting device such as a window, wall, orceiling.

Optical Phase Variation

In one embodiment, the film-based lightguide substantially maintains thespatial coherence of the input light. In another embodiment, the spatialphase of the light propagating through the lightguide or prior topropagating through the lightguide is adjusted to compensate for phasevariation upon propagating through the lightguide. In one embodiment,the light input surface of a light input coupler in a film-basedlightguide receives light with a first wavefront, the light propagatesthrough the film-based lightguide and exits the light emitting area ofthe film-based lightguide with a second wavefront, wherein the firstwavefront and the second wavefront have an interferometric visibilitygreater than one selected from the group 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9, and 0.95. The interferometric visibility is the difference betweenthe maximum and minimum fringe intensity divided by the sum of themaximum and minimum fringe intensity across the area of theinterference. In this embodiment, the fringe intensity can be measuredby combining and interfering light from the light source that has notpassed through the film-based lightguide with the light output from thefilm-based lightguide. In one embodiment, the light exiting the lightemitting region of the lightguide has a first phase variation across thelight emitting area less than one selected from the group: 60, 50, 40,30, 20, 10, 5, 3, 2, 1, and 0.5 degrees. In one embodiment, a phasecompensating element is positioned to receive light from the one or morelight sources and transmit light that enters into the light inputcoupler input surface. In this embodiment, the phase compensatingelement can compensate for the variation in phase (due to different pathlengths of travel within the coupling lightguides, for example) suchthat the phase output from the light emitting region of the lightguidehas a first phase variation across the light emitting region. In oneembodiment, the phase compensating element is a light transmittingelement where the thickness varies in the input plane or surface for thelight input coupler. In one embodiment, the phase compensating elementcomprises a shape or region with a shape or feature comprising one ormore selected from the group: wedge, tapered element, stepped wedgeelement, sheet with a thickness varying in two directions orthogonal tothe thickness, sheet with a thickness varying in one directionorthogonal to the thickness, printed retarder, printed waveplate,microstructured optical element, diffractive optical element, andprinted optical element. In another embodiment, the phase compensationelement comprises one or more coatings or elements added to the opticalpath of the light propagating within the coupling lightguides, lightmixing region, or light emitting region. For example, in one embodiment,a coating of a first material is applied in different lengths and/orthicknesses on the surface of a plurality of coupling lightguides suchthat light propagating through the coupling lightguides has a longerpath length due to propagating through the coatings (two passes at eachreflection). In this manner, coatings can be individually applied todifferent coupling lightguides to adjust the phase output. Similarly,coatings with different thickness, sizes/shapes, or materials withdifferent refractive indexes could be applied to different regions ofthe light mixing region and/or the light emitting region to adjust thephase output and phase variation of the light emitting from the lightemitting device or display.

In one embodiment, the phase variation across the light emitting area,region of the light emitting area, or display is measured and a phasecompensation element is added to the light emitting device to compensatefor the phase variation (or path length difference through differentregions and/or coupling lightguide lengths) and generate a second phasevariation (or path length difference) less than the first phasevariation. In another embodiment, the relative phase variation acrossthe light emitting area of the light output from the light emitting areais less than the first phase variation and the light emitting devicecomprises a reflective optical element such as a reflective liquidcrystal on silicon display positioned to receive the light output fromthe light emitting area of the lightguide.

In another embodiment, the low angle directing features or the lightturning features are positioned along the direction of light propagationin the lightguide such that the light extracted from the light emittingarea of the lightguide has a uniform, constant, predetermined, orcontrolled phase due to the control of the path length of the lightpropagating in the lightguide. For example, in this embodiment, the pathlength for light propagating through a relatively short couplinglightguide may be increased by extracting the light further along in thepropagation direction in the light emitting area (at the far side of thelight emitting area) to adjust the phase of the light output.

Optical Path Length Variation

In one embodiment, the optical path length variation across the lightemitting area, region of the light emitting area, or display is measuredand one or more path length compensation elements are added to the lightemitting device to compensate for the path length difference for lightpropagating through different regions and/or coupling lightguidelengths.

In one embodiment, a path length compensating element is positioned toreceive light from the one or more light sources and transmit light thatenters into the light input coupler input surface. In this embodiment,the path length compensating element can compensate for the variation inpath lengths of travel within the lightguide, light mixing region andcoupling lightguides such that the variation in path length of lightexiting the light emitting region of the lightguide is less than a firstpath length variation. In one embodiment, the first path lengthvariation across the light emitting area of the film-based lightguidefrom the light input surface is less than one selected from the group: 1meter, 0.5 meters, 0.2 meters, 10 centimeters, 5 centimeters, 1centimeter, 5 millimeters, 2 millimeters, 1 millimeter, 500 microns, 200microns, 100 microns, 50 microns, 20 microns, 10 microns, 5 microns, 1micron and 500 nanometers. For example in one embodiment, a largefilm-based lightguide is used to illuminate a 5 meter sized object witha depth of 5 meters with laser light for a transmission hologram and thepath length difference across the large light emitting area should beless than the coherence length of the laser (which could be 10 meters)and less than the depth (5 meters) of the object to be recorded to allowfor high contrast interference fringes. Similarly, a digital holographicrecording of a microscopic cellular event may require maintaining a verylow (on the order of tens of microns) variation of path lengthdifference across the light emitting area. In one embodiment, the lightsource is a laser with a beam expanded and collimated to illuminate aspatial light modulator.

In one embodiment, the path length compensating element is a lighttransmitting element where the thickness varies in the input plane orsurface for the light input coupler. In one embodiment, the path lengthcompensating element comprises a shape or region with a shape or featurecomprising one or more selected from the group: wedge, tapered element,stepped wedge element, sheet with a thickness varying in two directionsorthogonal to the thickness, sheet with a thickness varying in onedirection orthogonal to the thickness, printed retarder, printedwaveplate, microstructured optical element, diffractive optical element,and printed optical element. In another embodiment, the path lengthcompensation element comprises one or more coatings or elements added tothe optical path of the light propagating within the couplinglightguides, light mixing region, or light emitting region. For example,in one embodiment, a coating of a first material is applied in differentlengths and/or thicknesses on the surface of a plurality of couplinglightguides such that light propagating through the coupling lightguideshas a longer path length due to propagating through the coatings (twopasses at each reflection). In this manner, coatings can be individuallyapplied to different coupling lightguides to adjust the path lengthdifference across the light emitting region. Similarly, coatings withdifferent thickness, sizes/shapes, or materials with differentrefractive indexes could be applied to different regions of the lightmixing region and/or the light emitting region to adjust the path lengthvariation of the light emitting from the light emitting area, lightemitting device, or light emitting display.

Soft or Shock Absorbing Lightguide, Cladding or Adhesive

In one embodiment, the lightguide, cladding, or adhesive opticallycoupled to the lightguide includes a pliable or impact absorbingmaterial. In this embodiment, the lightguide or adhesive opticallycoupled to the lightguide (such as the adhesive used to bond thelightguide to the electro-optical region of the display) can function toabsorb impact or other external pressure on the display or active areaof the display. In another embodiment, the lightguide, the adhesive, ora component physically and/or optically coupled to the lightguideincludes a surface relief profile and the display has a higher ASTMD1709-09 impact strength than would a lightguide or component of athickness the same as the region of the lightguide or component withoutthe surface relief profile. In one embodiment, the ASTM D2240 Shore Ahardness of the light transmitting lightguide, adhesive, or componentphysically and/or optically coupled to the lightguide is greater thanone selected from the group: 5, 10, 20, 30, 40, 50, 60, 70, and 80. Inone embodiment, the light emitting device includes an adhesive thatconforms to a non-planar color filter array. In a further embodiment,the adhesive is vacuum filed into a region between the lightguide andthe electro-optical material of the display. In another embodiment, theadhesive is a pressure sensitive adhesive, two-part epoxy, UV curableadhesive, thermoset adhesive, silicone adhesive, acrylate-basedadhesive, UV curable pressure sensitive adhesive, or thermally settingadhesive. In another embodiment, at least one of the surfaces of thefilm-based lightguide; cladding layer of the film based lightguide;touchscreen layer or substrate; hardcoating layer or substrate;anti-glare layer or substrate; color filter layer or substrate;electro-optic layer or substrate; reflective material, film, layer, orsubstrate; polarizer layer or substrate; light redirecting layer orsubstrate; light extraction feature film, layer or substrate; impactprotection layer or substrate; internal coating or layer; conformalcoating or layer; circuit board or layer; thermally conducting film,layer or substrate; sealant layer or substrate; spacer layer orsubstrate; electrically conducting layer (transparent or opaque) orsubstrate; anode layer or substrate; cathode layer or substrate; activematrix layer or substrate; and passive matrix layer or substrate ismodified by coating, spraying, sputtering, electroplating, sputterdeposition, electrophoretic deposition, chemical vapor deposition,mechanical plating, physical vapor deposition, vacuum plating, chemicalsurface treatment, or plasma surface treatment (atmospheric, flame, orchemical). In one embodiment, the aforementioned modification reducesthe size or apparent size of display artifacts, improves the displayappearance, increases adhesion or wettability with the adhesive,increases wettability with other components of the light emitting device(such as color filter materials, electro-optical materials, inks, andsealants), increases corrosion resistance, increases tarnish resistance,increases chemical resistance, increases wear resistance, increaseshardness, increases or decreases electrical conductivity, removessurface flaws, or increases or decrease the surface tension.

Light Redirecting Element Disposed to Redirect Light from the Lightguide

In one embodiment, a light emitting device includes a lightguide withlight redirecting elements disposed on or within the lightguide andlight extraction features disposed in a predetermined relationshiprelative to one or more light redirecting elements. In anotherembodiment, a first portion of the light redirecting elements aredisposed above a light extraction feature in a direction substantiallyperpendicular to the light emitting surface, lightguide, or lightguideregion.

In a further embodiment, light redirecting elements are disposed toredirect light which was redirected from a light extraction feature suchthat the light exiting the light redirecting elements is one selectedfrom the group of more collimated than a similar lightguide with asubstantially planar surface; has a full angular width at half maximumintensity less than 60 degrees, 50 degrees, 40 degrees, 30 degrees, 20degrees, 10 degrees, or 5 degrees in a first light output plane; has afull angular width at half maximum intensity less than 60 degrees, 50degrees, 40 degrees, 30 degrees, 20 degrees, 10 degrees, or 5 degrees ina first light output plane and second light output plane orthogonal tothe first output plane; and has a full angular width at half maximumintensity less than 60 degrees, 50 degrees, 40 degrees, 30 degrees, 20degrees, 10 degrees, or 5 degrees in all planes parallel to the opticalaxis of the light emitting device.

In one embodiment, the lightguide comprises a substantially linear arrayof lenticules disposed on at least one surface opposite a substantiallylinear array of light extraction features wherein the light redirectingelement collimates a first portion of the light extracted from thelightguide by the light extraction features. In a further embodiment, alight emitting device comprises a lenticular lens film lightguidefurther comprising coupling lightguides, wherein the couplinglightguides are disposed substantially parallel to the lenticules at thelightguide region or light mixing region and the lenticular lens filmfurther comprises linear regions of light reflecting ink lightextraction features disposed substantially opposite the lenticules onthe opposite surface of the lenticular lens film lightguide and thelight exiting the light emitting device is collimated. In a furtherembodiment, the light extraction features are light redirecting features(such as TIR grooves or linear diffraction gratings) that redirect lightincident within one plane significantly more than light incident from aplane orthogonal to the first plane. In one embodiment, a lenticularlens film comprises grooves on the opposite surface of the lenticulesoriented at a first angle greater than 0 degrees to the lenticules.

In another embodiment, a light emitting device comprises a microlensarray film lightguide with an array of microlenses on one surface andthe film further comprises regions of reflecting ink light extractionfeatures disposed substantially opposite the microlenses on the oppositesurface of the lenticular lens film lightguide and the light exiting thelight emitting device is substantially collimated or has an angular FWHMluminous intensity less than 60 degrees. A microlens array film, forexample, can collimate light from the light extraction features inradially symmetric directions. In one embodiment, the microlens arrayfilm is separated from the lightguide by an air gap.

The width of the light extraction features (reflecting line of ink inthe aforementioned lenticular lens lightguide film embodiment) willcontribute to the degree of collimation of the light exiting the lightemitting device. In one embodiment, light redirecting elements aredisposed substantially opposite light extraction features and theaverage width of the light extraction features in a first directiondivided by the average width in a first direction of the lightredirecting elements is less than one selected from the group of 1, 0.9,0.7, 0.5, 0.4, 0.3, 0.2, and 0.1. In a further embodiment, the focalpoint of collimated visible light incident on a light redirectingelement in a direction opposite from the surface comprising the lightextraction feature is within at most one selected from the group of 5%,10%, 20%, 30%, 40%, 50% and 60% of the width of light redirectingelement from the light extraction feature. In another embodiment, thefocal length of at least one light redirecting element or the averagefocal length of the light redirecting elements when illuminated bycollimated light from the direction opposite the lightguide is less thanone selected from the group of 1 millimeter, 500 microns, 300 microns,200 microns, 100 microns, 75 microns, 50 microns and 25 microns.

In one embodiment, the focal length of the light redirecting elementdivided by the width of the light redirecting element is less than oneselected from the group of 3, 2, 1.5, 1, 0.8, and 0.6. In anotherembodiment, the optical f-number of the light redirecting elements isless than one selected from the group of 3, 2, 1.5, 1, 0.8, and 0.6. Inanother embodiment, the light redirecting element is a linear Fresnellens array with a cross-section of refractive Fresnel structures. Inanother embodiment, the light redirecting element is a linearFresnel-TIR hybrid lens array with a cross-section of refractive Fresnelstructures and totally internally reflective structures.

In a further embodiment, light redirecting elements are disposed toredirect light which was redirected from a light extraction feature suchthat a portion of the light exiting the light redirecting elements isredirected with an optical axis at an angle greater than 0 degrees fromthe direction perpendicular to the light emitting region, lightguideregion, lightguide, or light emitting surface. In another embodiment,the light redirecting elements are disposed to redirect light which wasredirected from a light extraction feature such that the light exitingthe light redirecting elements is redirected to an optical axissubstantially parallel to the direction perpendicular to the lightemitting region, lightguide region, lightguide, or light emittingsurface. In a further embodiment, the light redirecting elementdecreases the full angular width at half maximum intensity of the lightincident on a region of the light redirecting element and redirects theoptical axis of the light incident to a region of the light redirectingelement at a first angle to a second angle different than the firstangle.

In another embodiment, the angular spread of the light redirected by thelight extraction feature is controlled to optimize a light controlfactor. One light control factor is the percentage of light reaching aneighboring light redirecting element which could redirect light into anundesirable angle. This could cause side-lobes or light output intoundesirable areas. For example, a strongly diffusively reflectivescattering light extraction feature disposed directly beneath alenticule in a lenticular lens array may scatter light into aneighboring lenticule such that there is a side lobe of light at higherangular intensity which is undesirable in an application desiringcollimated light output. Similarly a light extraction feature whichredirects light into a large angular range such as a hemispherical domewith a relatively small radius of curvature may also redirect light intoneighboring lenticules and create side-lobes. In one embodiment, theBidirectional Scattering Distribution Function (BSDF) of the lightextraction feature is controlled to direct a first portion of incidentlight within a first angular range into a second angular range into thelight redirecting element to create a predetermined third angular rangeof light exiting the light emitting device.

Light Redirecting Element

As used herein, the light redirecting element is an optical elementwhich redirects a portion of light of a first wavelength range incidentin a first angular range into a second angular range different than thefirst. In one embodiment, the light redirecting element includes atleast one element selected from the group: refractive features, totallyinternally reflected feature, reflective surface, prismatic surface,microlens surface, diffractive feature, holographic feature, diffractiongrating, surface feature, volumetric feature, and lens. In a furtherembodiment, the light redirecting element includes a plurality of theaforementioned elements. The plurality of elements may be in the form ofa 2-D array (such as a grid of microlenses or close-packed array ofmicrolenses), a one-dimensional array (such as a lenticular lens array),random arrangement, predetermined non-regular spacing, semi-randomarrangement, or other predetermined arrangement. The elements mayinclude different features, with different surface or volumetricfeatures or interfaces and may be disposed at different thicknesseswithin the volume of the light redirecting element, lightguide, orlightguide region. The individual elements may vary in the x, y, or zdirection by at least one selected from the group: height, width,thickness, position, angle, radius of curvature, pitch, orientation,spacing, cross-sectional profile, and location in the x, y, or z axis.In one embodiment, the light redirecting element comprises light turningfeatures.

In one embodiment, the light redirecting element is optically coupled tothe lightguide in at least one region. In another embodiment, the lightredirecting element, film, or layer comprising the light redirectingelement is separated in a direction perpendicular to the lightguide,lightguide region, or light emitting surface of the lightguide by an airgap. In a further embodiment, the lightguide, lightguide region, orlight emitting surface of the lightguide is disposed substantiallybetween two or more light redirecting elements. In another embodiment, acladding layer or region is disposed between the lightguide orlightguide region and the light redirecting element. In anotherembodiment, the lightguide or lightguide region is disposed between twolight redirecting elements wherein light is extracted from thelightguide or lightguide region from both sides and redirected by lightredirecting elements. In this embodiment, a backlight may be designed toemit light in opposite directions to illuminate two displays, or thelight emitting device could be designed to emit light from one side ofthe lightguide by adding a reflective element to reflect light emittedout of the lightguide in the opposite direction back through thelightguide and out the other side.

In another embodiment, the average or maximum dimension of an element ofa light redirecting element in at least one output plane of the lightredirecting element is equal to or less than one selected from the groupof 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, and 10% the average ormaximum dimension of a pixel or sub-pixel of a spatial light modulatoror display. In another embodiment, a backlight comprises lightredirecting elements that redirect light to within a FWHM of 30 degreestoward a display wherein each pixel or sub-pixel of the display receiveslight from two or more light redirecting elements.

In another embodiment, the light redirecting element is a collection ofprisms disposed to refract and totally internally reflect light towardthe spatial light modulator. In one embodiment, the collection of prismsis a linear array of prisms with an apex angle between 50 degrees and 70degrees. In another embodiment, the collection of prisms is a lineararray of prisms with an apex angle between 50 degrees and 70 degrees towhich a light transmitting material has been applied or disposed betweenthe prisms and the lightguide or lightguide region within regions suchthat the film is effectively planarized in these regions and thecollection of prisms is now a two-dimensionally varying arrangement ofprisms (thus on the surface it no longer appears to be a linear array).Other forms of light redirecting elements, reverse prisms, hybridelements, with refractive or totally internally reflective features, ora combination thereof, may be used in one embodiment. Modifications ofelements such as “wave-like” variations, variations in size, dimensions,shapes, spacing, pitch, curvature, orientation and structures in the x,y, or z direction, combining curved and straight sections, etc. areknown in the art. Such elements are known in the area of backlights andoptical films for displays and include those disclosed in “Optical filmto enhance cosmetic appearance and brightness in liquid crystaldisplays,” Lee et al., OPTICS EXPRESS, 9 Jul. 2007, Vol. 15, No. 14, pp.8609-8618; “Hybrid normal-reverse prism coupler for light-emitting diodebacklight systems,” Aoyama et al., APPLIED OPTICS, 1 Oct. 2006, Vol. 45,No. 28, pp. 7273-7278; Japanese Patent Application No. 2001190876,“Optical Sheet,” Kamikita Masakazu; U.S. patent application Ser. No.11/743,159; U.S. Pat. Nos. 7,085,060, 6,545,827, 5,594,830, 6,151,169,6,746,130, and 5,126,882. In a further embodiment, at least one lightextraction feature is centered in a first plane off-axis from the axisof the light redirecting element. In this embodiment, a portion of thelight extraction feature may intersect the optical axis of the lightextraction feature or it may be disposed sufficiently far from theoptical axis that it does not intersect the optical axis of the lightextraction feature. In another embodiment, the distance between thecenters of the light extraction features and the corresponding lightredirecting elements in first plane varies across the array orarrangement of light redirecting elements.

In one embodiment, the locations of the light extraction featuresrelative to the locations of the corresponding light redirectingelements varies in at least a first plane and the optical axis of thelight emitted from different regions of the light emitting surfacevaries relative to the orientation of the light redirecting elements. Inthis embodiment, for example, light from two different regions of aplanar light emitting surface can be directed in two differentdirections. In another example of this embodiment, light from twodifferent regions (the bottom and side regions, for example) of a lightfixture with a convex curved light emitting surface directed downwardsis directed in the same direction (the optical axes of each region aredirected downwards toward the nadir wherein the optical axis of thelight redirecting elements in the bottom region are substantiallyparallel to the nadir, and the optical axis of the light redirectingelements in the side region are at an angle, such as 45 degrees, fromthe nadir). In another embodiment, the location of the light extractionfeatures are further from the optical axes of the corresponding lightredirecting elements in the outer regions of the light emitting surfacein a direction perpendicular to lenticules than the central regionswhere the light extraction regions are substantially on-axis and thelight emitted from the light emitting device is more collimated.Similarly, if the light extraction features are located further from theoptical axes of the light redirecting elements in a direction orthogonalto the lenticules from a first edge of a light emitting surface, thelight emitted from the light emitting surface can be directedsubstantially off-axis. Other combinations of locations of lightextraction features relative to light redirecting elements can readilybe envisioned including varying the distance of the light extractionfeatures from the optical axis of the light redirecting element in anonlinear fashion, moving closer to the axis then further from the axisthen closer to the axis in a first direction, moving further from theaxis then closer to the axis then further to the axis in a firstdirection, upper and lower apexes of curved regions of a light emittingsurface with a sinusoidal-like cross-sectional (wave-like) profilehaving light extraction features substantially on-axis and the walls ofthe profile having light extraction features further from the opticalaxis of the light redirecting elements, regular or irregular variationsin separation distances of the light extraction features from theoptical axes of the light redirecting elements, etc.

Angular Width Control

In one embodiment, the widths of the light extraction features relativeto the corresponding widths of the light redirecting elements varies inat least a first plane and the full angular width at half maximumintensity of the light emitted from the light redirecting elementsvaries in at least a first plane. For example, in one embodiment, alight emitting device comprises a lenticular lens array lightguide filmwherein the central region of the light emitting surface in a directionperpendicular to the lenticules comprises light extraction features thathave an average width of approximately 20% of the average width of thelenticules and the outer region of the light emitting surface in adirection perpendicular to the lenticules comprises light extractionfeatures with an average width of approximately 5% of the average widthof the lenticules and the angular full width at half maximum intensityof the light emitted from the central region is larger than that fromthe outer regions.

Off-Axes Light Redirection

In a further embodiment, the light redirecting element is disposed toreceive light from an electro-optical element wherein the opticalproperties may be changed in one or more regions, selectively or as awhole by applying a voltage or a current to the device. In oneembodiment, the light extraction features are regions of a polymerdispersed liquid crystal material wherein the light scattering from thelightguide in a diffuse state is redirected by the light redirectingelement. In another embodiment, the light extraction feature has a smallpassive region and a larger active region disposed to change fromsubstantially clear to substantially transmissive diffuse (forwardscattering) such that when used in conjunction with the lightredirecting element, the display can be changed from a narrow viewingangle display to a larger viewing angle display through the applicationor removal of voltage or current from the electro-optical region ormaterial. For example, lines of grooved light extraction features aredisposed adjacent (x, y, or z direction) a film comprising wider linespolymer dispersed liquid crystal (PDLC) material disposed to change fromsubstantially clear to substantially diffuse upon application of avoltage across the electrodes. Other electro-optical materials such aselectrophoretic, electro-wetting, electrochromic, liquid crystal,electroactive, MEMS devices, smart materials and other materials thatcan change their optical properties through application of a voltage,current, or electromagnetic field may also be used.

Location of the Film-Based Lightguide

In one embodiment, the core region of the film-based lightguide ispositioned between two layers selected from the group: hardcoatingsubstrate, layer, or adhesive; anti-glare layer or anti-reflectionlayer, substrate or adhesive; color filter material, layer, substrate,or adhesive; first cladding of the lightguide; second cladding of thelightguide; cladding substrate or adhesive; film-based lightguideadhesive; electro-optic layer (such as liquid crystal layer orelectrophoretic layer, for example); viewer side substrate for theelectro-optic layer; substrate for the electro-optic layer on non-viewerside; adhesive or substrate for the electro-optic layer; reflectivematerial, film, layer, or substrate or adhesive for reflective layer;polarizer layer substrate, or adhesive for polarizer; light redirectinglayer; light extraction feature film; impact protection layer; internalcoating; conformal coating; circuit board; flexible connector; thermallyconducting film, layer (such as a stainless steel, copper, or aluminumfoil layer), substrate, or adhesive; sealant layer, film substrate oradhesive; air gap layer; spacer layer or substrate for the spacer layer;electrically conducting layer (transparent or opaque), substrate, oradhesive; anode layer, substrate, or adhesive for anode layer; cathodelayer, substrate or adhesive for cathode layer; active matrix layer,substrate or adhesive for active matrix layer; passive matrix layer,substrate or adhesive for passive matrix layer; and touchscreen layer,substrate for touchscreen, or adhesive for touchscreen layer. In anotherembodiment, the film-based lightguide functions as one or more of theaforementioned layers in addition to propagating light in a waveguidecondition.

In one embodiment, the film based lightguide is positioned between thecolor filter layer and the electro-optical layer such that the parallaxeffects due to high angle light are minimized (thus resulting in highercontrast, greater resolution, or increased brightness). In anotherembodiment, the film-based lightguide is the substrate for the colorfilter material or layer. In another embodiment, the film-basedlightguide is the substrate for the electro-optic material or layer.

In one embodiment, the distance between the light extraction featuresand the color filters in a multi-color display is minimized bypositioning the film-based lightguide within the display or using thefilm-based lightguide as a substrate for a layer or material of thedisplay (such as, for example, the substrate for the color filter layer,transparent conductor layer, adhesive layer, or electro-optical materiallayer). In one embodiment, the light emitting device includes aplurality of light absorbing adhesive regions that adhere to one or morelayers of the display or film-based lightguide (such as on the claddinglayer of the film-based lightguide or on the electro-optical materiallayer).

In one embodiment, the light emitting device includes a film-basedlightguide and a force sensitive touchscreen wherein the film basedlightguide is sufficiently thin to permit a force sensitive touchscreento function by finger pressure on the display.

In one embodiment, a film-based lightguide frontlight is disposedbetween a touchscreen film and a reflective spatial light modulator. Inanother embodiment, a touchscreen film is disposed between thefilm-based lightguide and the reflective spatial light modulator. Inanother embodiment, the reflective spatial light modulator, thefilm-based lightguide frontlight and the touchscreen are all film-baseddevices and the individual films may be laminated together. In anotherembodiment, the light transmitting electrically conductive coating forthe touchscreen device or the display device is coated onto thefilm-based lightguide frontlight. In a further embodiment, thefilm-based lightguide is physically coupled to the flexible electricalconnectors of the display or the touchscreen. In one embodiment, theflexible connector is a “flexible cable”, “flex cable,” “ribbon cable,”or “flexible harness” including a rubber film, polymer film, polyimidefilm, polyester film or other suitable film.

In one embodiment, a reflective display includes one or more film-basedlightguides disposed within or adjacent to one or more regions selectedfrom the group: the region between the touchscreen layer and thereflective light modulating pixels, the region on the viewing side ofthe touchscreen layer, the region between a diffusing layer and thereflective light modulating pixels, the viewing side of the diffusinglayer in a reflective display, the region between a diffusing layer andthe light modulating pixels, the region between the diffusing layer andthe reflective element, the region between the light modulating pixelsand a reflective element, the viewing side of a substrate for acomponent or the light modulating pixels, the reflective display,between the color filters and the spatial light modulating pixels, theviewing side of the color filters, between the color filters and thereflective element, the substrate for the color filter, the substratefor the light modulating pixels, the substrate for the touchscreen, theregion between a protective lens and the reflective display, the regionbetween a light extraction layer and the light modulating pixels, theregion on the viewing side of a light extraction layer, the regionbetween an adhesive and a component of a reflective display, and betweentwo or more components of a reflective display known in the art. In theaforementioned embodiment, the film-based lightguide may includevolumetric light extraction features or light extraction features on oneor more surfaces of the lightguide and the lightguide may include one ormore lightguide regions, one or more cladding regions, or one or moreadhesive regions.

In one embodiment, the film-based lightguide is folded around a firstedge of the active area of a reflective spatial light modulator behind areflective spatial light modulator and one or more selected from thegroup: a touchscreen connector, touchscreen film substrate, reflectivespatial light modulator connector, and reflective spatial lightmodulator film substrate is folded behind the first edge, a second edgessubstantially orthogonal to the first edge, or an opposite edge to thefirst edge. In the aforementioned embodiment, a portion of thelightguide region, light mixing region, or coupling lightguide includesthe bend region of the fold and may extend beyond the reflective spatiallight modulator flexible connector, reflective spatial light modulatorsubstrate, touchscreen flexible connector or touchscreen flexiblesubstrate.

Orientation of Light within the Display

In one embodiment, a film-based lightguide illumination deviceilluminates a spatial light modulator (from the viewer side, from theside opposite the viewer, or from within the display) at a displayillumination angle within the layer or material adjacent theelectro-optical material or layer of the spatial light modulator in afirst illumination plane. As used herein, the display illumination angleis defined as the angle of peak intensity from the surface normal of thespatial light modulating component or layer measured (or calculated)within the layer or material adjacent (on the viewer side) the spatiallight modulating component or layer (such as for example, theelectro-optical elements of an electrophoretic display, or liquidcrystal layer in a liquid crystal display) in a first illuminationplane. In one embodiment, the display illumination angle is less thanone selected from the group: 60, 50, 40, 30, 20, 10, and 5 degrees. Inone embodiment, the first illumination plane is parallel to the extendeddirection of the coupling lightguides. In another embodiment, the firstillumination plane is perpendicular to the extended direction of thecoupling lightguides.

In another embodiment, a film-based lightguide illumination deviceilluminates a color filter layer or material (from the viewer side, fromthe side opposite the viewer, or from within the display) at a colorfilter illumination angle within the material or layer adjacent thecolor filter layer or material in a first illumination plane. As usedherein, the color filter illumination angle is defined as the angle ofpeak intensity from the surface normal of the color filter layer ormaterial measured (or calculated) within the layer or material adjacent(on the viewer side) the color filter layer or material (such as forexample, a red, green, and blue array of color filter materials in anelectrophoretic display) in a first illumination plane. In oneembodiment, the color filter illumination angle is less than oneselected from the group: 70, 60, 50, 40, 30, 20, 10, and 5 degrees.

As used herein, the lightguide illumination angle in a firstillumination plane is the peak angular intensity of light exiting thefilm-based lightguide (due to extraction features) measured orcalculated within the core layer (or within the cladding layer ifpresent) from the normal to the light emitting device surface (or normalto the film-based lightguide surface). In one embodiment, the lightguideillumination angle is less than one selected from the group: 70, 60, 50,40, 30, 20, 10, and 5 degrees in a first illumination plane. In oneembodiment the lightguide illumination angle is the same as the displayillumination angle or the color filter illumination angle.

In another embodiment, the angular bandwidth illumination angle is thefull angular width at half maximum intensity of the light exiting thefilm-based lightguide due to extraction features measured or calculatedwithin the core layer (or within the cladding layer if present) in afirst illumination plane from the normal to the light emitting devicesurface. In one embodiment, the angular bandwidth illumination angle isless than one selected from the group: 60, 50, 40, 30, 20, 10, and 5degrees in a first illumination plane.

By reducing the full angular width at half maximum intensity of thelight exiting the film-based lightguide due to extraction features orredirecting the light using extraction features such that the lightguideillumination angle, display illumination angle, or color filterillumination angle is closer to zero degrees, the resolution, contrast,and/or brightness of the display can be increased by reducing higherangle light that can pass through two light modulating pixels or colorfilters in a display.

In one embodiment, the light emitting device includes a lightcollimating optical element that reduces the full angular width at halfmaximum intensity of the light exiting the film-based lightguide byreducing the full angular width at half maximum intensity of the lightincident upon one or more light extraction features. In anotherembodiment, the thickness of the film-based lightguide is increased toallow for greater collimation in the plane normal to the surface of thefilm through the use of a larger light collimating optical element todirect light into the light input surface. In another embodiment, atleast one of the size, spacing, shape, depth, width, location, anddensity of the light extraction features is adjusted to reduce the fullangular width at half maximum intensity of the light exiting thefilm-based lightguide or direct the lightguide illumination angle,display illumination angle, or color filter illumination angle closer tozero degrees.

In one embodiment, a light extraction feature on the film-basedlightguide defines a recessed (concave) or protruding (convex) featureon the film surface, and a light absorbing material on the viewer sideof the recessed or protruding feature absorbs stray light reflecting,refracting or diffracting from the feature directly, therefore absorbingthe light that does not pass through the display that would reduce thedisplay contrast. In one embodiment, the light extracting feature is arefractive surface, diffractive surface, a total internal reflectionsurface, or a combination of one or more of these surfaces. In oneembodiment, the light extraction feature is defined by a plurality offacets, such as for example, two, three, or four linear facets pergroove, linear feature, two-dimensionally arrayed feature, orthree-dimensionally arrayed feature. In another embodiment, the lightextraction feature is defined in a separate layer or material andoptically coupled to the lightguide. In one embodiment, a lightabsorbing material with a first refractive index less than therefractive index of the core material is optically coupled to the coreor a cladding layer such that higher angle light is absorbed by thelight absorbing material. In one embodiment, the higher angle light isthe light traveling within the core region of the lightguide at an angleto the optical axis of the lightguide greater than one selected from thegroup 40, 50, 60, 70, 80, and 85 degrees.

In one embodiment, illumination from two or more sides of the lightemitting area of the film-based lightguide interacting with the lightextraction features reduces the full angular width at half maximumintensity of the light exiting the film-based lightguide or directs thelightguide illumination angle, display illumination angle, or colorfilter illumination angle closer to zero degrees.

In another embodiment, an adhesive layer adjacent to the recessed lightextraction features permits a gas or air cavity of a low refractiveindex that causes light propagating within the lightguide (or materialor layer that the extraction feature is formed within) to totallyinternally reflect at the interface between the lightguide (or materialor layer that the extraction feature is formed within) and the gas orair cavity at the light extraction feature. For example, in oneembodiment, a pressure sensitive adhesive layer is laminated onto afilm-based lightguide including groove cavities in a core region of thelightguide such that there is an air gap for total internal reflectionof the light within the lightguide at the extraction feature—air cavityinterface. In another embodiment, the thickness of the adhesive layeradjacent one or more cavity based light extraction features is less thanone selected from the group 2, 1.5, 1, 0.75, 0.5, 0.2, and 0.1 times thedepth of the light extraction feature in the thickness direction of thefilm. In another embodiment, the thickness of the adhesive adjacent oneor more cavity based light extraction features is less than one selectedfrom the group: 200, 175, 150, 125, 100, 75, 60, 50, 40, 30, 20, and 10microns. In another embodiment, the thickness of the cladding adjacentone or more cavity based light extraction features is less than oneselected from the group: 200, 175, 150, 125, 100, 75, 60, 50, 40, 30,20, and 10 microns.

In one embodiment, the full angular width at half maximum intensity ofthe light from the light source exiting the coupling lightguides isgreater in a first plane including the thickness direction of the filmthan in a second plane including the direction orthogonal to thethickness direction. In one embodiment, the light output profile fromthe light source is rotated such that the collimation or plane includingthe lowest divergence is rotated or switched within the light mixingregion, lightguide region, or light emitting region. In one embodiment,the light propagating within the film-based lightguide is redirected bylight redirecting features, internal light directing edges or opticalelements such that the full angular width at half maximum intensity ofthe light from the light source incident upon one or more lightextraction features is greater in the second plane than in the firstplane.

Light Emitting Device

In one embodiment, a light emitting device comprises: a film lightguideof a lightguide material with a lightguide refractive index n_(DL),including a body having a first surface and an opposing second surface;a plurality of coupling lightguides extending from the body, eachcoupling lightguide of the plurality of coupling lightguides having anend, the plurality of coupling lightguides folded and stacked such thatthe ends of the plurality of coupling lightguides define a light inputsurface; the body of the film comprising a first cladding layercomprising a first material with a first refractive index, n_(D1), asecond cladding layer comprising a second material with a secondrefractive index n_(D2) where n_(DL)>n_(D2)>n_(D1); a plurality of lowangle directing features optically coupled to the body of thelightguide; a plurality of light turning features optically coupled tothe lightguide, wherein light propagating under total internalreflection at a first angle within the lightguide is redirected by thelow angle directing features to a second angle less than the criticalangle of an interface between the core lightguide layer and the secondlayer, a portion of the redirected light propagating through theinterface and redirected by the light turning features to an anglewithin 30 degrees of the thickness direction of the film.

In this embodiment, light propagating within the core layer or region ofthe film-based lightguide in the light emitting region that undergoes alow angle light redirection, such as by a low angle directing feature,will preferentially leak or exit the core layer or region of thelightguide on the side with the second refractive index since it ishigher than the first refractive index and the critical angle is higher.In this embodiment, light deviating from angles higher than the criticalangle to smaller angles to the normal of the film surface (or core-layerinterface) will first pass the critical angle boundary on the side ofthe core layer or region optically coupled to the cladding layer orregion with the higher refractive index than the cladding layer orregion on the opposite side of the core region or layer.

In one embodiment, the low angle directing feature is configured todeviate light by a total angle of deviation less than a maximum firsttotal angle of deviation θ_(f), from the angle of incidence, followingthe equation: θ_(f)=θ_(c2)−θ_(c1), where θ_(c2) is the critical anglebetween the core layer or region and the second cladding layer or regionand can also be expressed as θ_(c2)=sin⁻¹(n_(D2)/n_(DL)), and θ_(c1) isthe critical angle between the core layer or region and the firstcladding layer or region and can be expressed asθ_(c1)=sin⁻¹(n_(D1)/n_(DL)). In another embodiment, the low angledirecting feature is configured to provide a maximum total angle ofdeviation, θ_(max) of less than 110% of the maximum first total angle ofdeviation or θ_(max)<1.1×θ_(f). In another embodiment, the low angledirecting feature is configured to provide an average first total angleof deviation, θ_(fave), from the angle of incidence ofθ_(fave)=θ_(c2)−θ_(c1). In another embodiment, the low angle directingfeature is configured to provide an average total angle of deviation,θ_(ave) of less than 110% of the average first total angle of deviationor θ_(ave)<1.1×θ_(fave).

For example, in one embodiment, the first material has a refractiveindex of n_(D1)=1.4, the second material has a refractive index ofn_(D2)=1.5, and the core layer or region material has a refractive indexof n_(DL)=1.6. In this example, a low angle light directing featurecomprises an angled reflective surface wherein the angle of the surfacecauses a total light deviation less than θ_(f) such that the lightpreferentially escapes the core layer of the lightguide through thehigher index cladding layer or region. In this example, θ_(c1)=61degree, θ_(c2)=70 degrees, and thus the maximum first total angle ofdeviation for optimum coupling into the second cladding region is lessthan 9 degrees. Since light reflecting from an angled surface undergoesa total angle of deviation of twice the angle of the feature, the angleof the features are chosen to be less than 4.5 degrees

$\left( \frac{\theta_{f}}{2} \right)$from the direction perpendicular to the thickness direction of the filmat the feature. In one embodiment the average angle from a directionperpendicular to the thickness direction of the film at the feature ofthe surface of a reflective low angle directing feature receiving lightpropagating within the lightguide is less than

$\left( \frac{\theta_{f}}{2} \right)$degrees or less than

$1.1 \times \left( \frac{\theta_{f}}{2} \right)$degrees. In another embodiment, the thickness of the core layer orregion of the film-based lightguide is less than 100 microns and the lowangle directing feature directs (such as by reflection or refraction,for example) less than one selected from the group 100%, 80%, 60%, 40%,30%, 20%, 10%, and 5% of the incident light in a single interaction(such as a single reflection or single refraction, for example). In afurther embodiment, the light propagating within the lightguide thatinteracts with the low angle light directing features and propagates tothe light turning features interacts with an average of more than 1, 2,3, 4, 5, 10, 15, or 20 low angle directing features before reaching alight turning feature.

In one embodiment, the ratio of the length of the light emitting regionin the direction of light propagating from the first side to the secondside of the light emitting region to the average thickness of the lightemitting region is greater than one selected from the group: 300, 500,1000, 5,000, 7,000, 10,000, 15,000, and 20,000.

Backlight or Frontlight

In one embodiment, the film-based lightguide illuminates a display,forming an electroluminescent display. In one embodiment, the film basedlightguide is a frontlight for a reflective or transflective display. Inanother embodiment, the film-based lightguide is a backlight for atransmissive or transflective display. Typically, with displaysincluding light emitting lightguides for illumination, the location ofthe lightguide will determine whether or not it is considered abacklight or frontlight for an electroluminescent display wheretraditionally a frontlight lightguide is a lightguide disposed on theviewing side of the display (or light modulator) and a backlightlightguide is a lightguide disposed on the opposite side of the display(or light modulator) than the viewing side. However, the frontlight orbacklight terminology to be used can vary in the industry depending onthe definition of the display or display components, especially in thecases where the illumination is from within the display or withincomponents of the spatial light modulator (such as the cases where thelightguide is disposed in-between the liquid crystal cell and the colorfilters or in-between the liquid crystal materials and a polarizer in anLCD). In some embodiments, the lightguide is sufficiently thin to bedisposed within a spatial light modulator, such as between lightmodulating pixels and a reflective element in a reflective display. Inthis embodiment, light can be directed toward the light modulatingpixels directly or indirectly by directing light to the reflectiveelement such that is reflects and passes through the lightguide towardthe spatial light modulating pixels. In one embodiment, a lightguideemits light from one side or both sides and with one or two lightdistribution profiles that contribute to the “front” and/or “rear”illumination of light modulating components. In embodiments disclosedherein, where the light emitting region of the lightguide is disposedbetween the spatial light modulator (or electro-optical regions of thepixels, sub-pixels, or pixel elements) and a reflective component of areflective display, the light emitting from the light emitting regionmay propagate directly toward the spatial light modulator or indirectlyvia directing the light toward a reflective element such that the lightreflected passes back through the lightguide and into the spatial lightmodulator. In this specific case, the terms “frontlight” and “backlight”used herein may be used interchangeably.

In one embodiment, a light emitting display backlight or frontlightincludes a light source, a light input coupler, and a lightguide. In oneembodiment, the frontlight or backlight illuminates a display or spatiallight modulator selected from the group: transmissive display,reflective display, liquid crystal displays (LCD's), MEMs based display,electrophoretic displays, cholesteric display, time-multiplexed opticalshutter display, color sequential display, interferometric modulatordisplay, bistable display, electronic paper display, LED display, TFTdisplay, OLED display, carbon nanotube display, nanocrystal display,head mounted display, head-up display, segmented display, passive matrixdisplay, active matrix display, twisted nematic display, in-planeswitching display, advanced fringe field switching display, verticalalignment display, blue phase mode display, zenithal bistable device,reflective LCD, transmissive LCD, electrostatic display, electrowettingdisplay, bistable TN displays, micro-cup EPD displays, grating alignedzenithal display, photonic crystal display, electrofluidic display, andelectrochromic displays.

LCD Backlight or Frontlight

In one embodiment, a backlight or frontlight suitable for use with aliquid crystal display panel includes at least one light source, lightinput coupler, and lightguide. In one embodiment, the backlight orfrontlight includes a single lightguide wherein the illumination of theliquid crystal panel is white. In another embodiment, the backlight orfrontlight includes a plurality of lightguides disposed to receive lightfrom at least two light sources with two different color spectra suchthat they emit light of two different colors. In another embodiment, thebacklight or frontlight includes a single lightguide disposed to receivelight from at least two light sources with two different color spectrasuch that they emit light of two different colors. In anotherembodiment, the backlight or frontlight includes a single lightguidedisposed to receive light from a red, green and blue light source. Inone embodiment, the lightguide includes a plurality of light inputcouplers wherein the light input couplers emit light into the lightguidewith different wavelength spectrums or colors. In another embodiment,light sources emitting light of two different colors or wavelengthspectrums are disposed to couple light into a single light inputcoupler. In this embodiment, more than one light input coupler may beused and the color may be controlled directly by modulating the lightsources.

In a further embodiment, the backlight or frontlight includes alightguide disposed to receive light from a blue or UV light emittingsource and further includes a region including a wavelength conversionmaterial such as a phosphor film. In another embodiment, the backlightincludes 3 layers of film lightguides wherein each lightguideilluminates a display with substantially uniform luminance when thecorresponding light source is turned on. In this embodiment, the colorgamut can be increased by reducing the requirements of the color filtersand the display can operate in a color sequential mode or all-colors-onsimultaneously mode. In a further embodiment, the backlight orfrontlight includes 3 layers of film lightguides with 3 spatiallydistinct light emitting regions including light extraction featureswherein each light extraction region for a particular lightguidecorresponds to a set of color pixels in the display. In this embodiment,by registering the light extracting features (or regions) to thecorresponding red, green, and blue pixels (for example) in a displaypanel, the color filters are not necessarily needed and the display ismore efficient. In this embodiment, color filters may be used, however,to reduce crosstalk.

In a further embodiment, the light emitting device includes a pluralityof lightguides (such as a red, green and blue lightguide) disposed toreceive light from a plurality of light sources emitting light withdifferent wavelength spectrums (and thus different colored light) andemit the light from substantially different regions corresponding todifferent colored sub-pixels of a spatial light modulator (such as anLCD panel), and further includes a plurality of light redirectingelements disposed to redirect light from the lightguides towards thespatial light modulator. For example, each lightguide may include acladding region between the lightguide and the spatial light modulatorwherein light redirecting elements such as microlenses are disposedbetween the light extraction features on the lightguide and the spatiallight modulator and direct the light toward the spatial light modulatorwith a FWHM of less than 60 degrees, a FWHM of less than 30 degrees, anoptical axis of emitted light within 50 degrees from the normal to thespatial light modulator output surface, an optical axis of emitted lightwithin 30 degrees from the normal to the spatial light modulator outputsurface, or an optical axis of emitted light within 10 degrees from thenormal to the spatial light modulator output surface. In a furtherembodiment, an arrangement of light redirecting elements are disposedwithin a region disposed between the plurality of lightguides and thespatial light modulator to reduce the FWHM of the light emitted from theplurality of lightguides. The light redirecting elements arranged withina region, such as on the surface of a film layer, may have similar ordissimilar light redirecting features. In one embodiment, the lightredirecting elements are designed to redirect light from lightextraction features from a plurality of lightguides into FWHM angles oroptical axes within 10 degrees of each other. For example, a backlightincluding a red, green, and blue film-based lightguides may include anarray of microlenses with different focal lengths substantially near the3 depths of the light extraction features on the 3 lightguides. In oneembodiment, lightguide films less than 100 microns thick enable lightredirecting elements to be closer to the light extraction features onthe lightguide and therefore capture more light from the lightextraction feature. In another embodiment, a light redirecting elementsuch as a microlens array with substantially the same light redirectionfeatures (such as the same radius of curvature) may be used with thinlightguides with light extraction features at different depths since thedistance between the nearest corresponding light extraction feature andfarthest corresponding light extraction feature in the thicknessdirection is small relative to the diameter (or a dimension) of thelight redirecting element, pixel, or sub-pixel.

Reflective Display

In one embodiment, a method of producing a display includes: forming anarray of coupling lightguides from a lightguide region of a filmincluding a core region and a cladding region by separating the couplinglightguides from each other such that they remain continuous with thelightguide region of the film and include bounding edges at the end ofthe coupling lightguides; folding the plurality of coupling lightguidessuch that the bounding edges are stacked; directing light from a lightsource into the stacked bounding edges such that light from the lightsource propagates within the core region through the couplinglightguides and lightguide region of the film by total internalreflection; forming light extraction features on or within the corelayer in a light emitting region of the lightguide region of the film;disposing a light extracting region on the cladding region or opticallycoupling a light extracting region to the cladding region in a lightmixing region of the lightguide region between the coupling lightguidesand the light emitting region; and disposing the light emitting regionadjacent a reflective spatial light modulator.

The lightguides disclosed herein may be used to illuminate a reflectivedisplay. In one embodiment, a reflective display comprises a firstreflective surface and a film-based lightguide comprising a plurality ofcoupling lightguides. In this embodiment, the reflective display may bea diffusely reflective spatial light modulator or a specularlyreflecting spatial light modulator. For example, a diffusely reflectivespatial light modulator can include a reflective display such as anelectrophoretic particle based reflective display and a specularlyreflecting spatial light modulator can include a reflective LCD withspecularly reflecting rear electrodes. The reflective spatial lightmodulator, or a component of the light emitting device, lightguide, or acoating or layer positioned within, may include a light scattering ordiffusive surface or volumetric light scattering particles or domains.

In one embodiment, the light emitting device is a frontlight for a watchthat comprises a reflective display. In another embodiment, the largestdimension in a plane orthogonal to the thickness direction of thelightguide or display of the light emitting region is less than oneselected from the group of 100, 75, 50, 40, 30, and 25 millimeters.

Modes of the Light Emitting Device

In another embodiment, a light emitting device includes one or moremodes selected from the group: normal viewing mode, daytime viewingmode, high brightness mode, low brightness mode, nighttime viewing mode,night vision or NVIS compatible mode, dual display mode, monochromemode, grayscale mode, transparent mode, full color mode, high colorgamut mode, color corrected mode, redundant mode, touchscreen mode, 3Dmode, field sequential color mode, privacy mode, video display mode,photo display mode, alarm mode, nightlight mode, emergency lighting/signmode. The daytime viewing mode may include driving the device (such as adisplay or light fixture) at a high brightness (greater than 300 Cd/m2for example) and may include using two or more lightguides, two or morelight input couplers, or driving additional LEDs at one or more lightinput couplers to produce the increase in brightness. The nighttimeviewing mode may include driving the device at a low brightness (lessthan 50 Cd/m2 for example). The dual display mode may include abacklight (or frontlight) wherein the lightguide illuminates more thanone spatial light modulator or display. For example, in a cellphonewhere there are two displays in a flip configuration, each display canbe illuminated by the same film lightguide that emits light toward eachdisplay. In a transparent mode, the lightguide may be designed to besubstantially transparent such that one can see through the display orbacklight. In another embodiment, the light emitting device includes atleast one lightguide for a first mode, and a second backlight for asecond mode different than the first mode. For example, the transparentmode backlight lightguide on a device may have a lower light extractionfeature density, yet enable see-through. For a high brightness mode onthe same device, a second lightguide may provide increased displayluminance relative to the transparent mode. The increased color gamutmode may provide an increased color gamut (such as greater than 100%NTSC) by using one or more spectrally narrow colored LEDs or lightsources. These LEDs used in the high color gamut mode may provideincreased color gamut by illumination through the same or differentlightguide or light input coupler. The color corrected mode maycompensate for light source color variation over time (such as phosphorvariation), LED color binning differences, or due to temperature or theenvironment. The touchscreen mode may allow one or more lightguides tooperate as an optical frustrated TIR based touchscreen. The redundantbacklight mode may include one or more lightguides or light sources thatcan operate upon failure or other need. The 3D mode for the lightemitting device may include a display and light redirecting elements ora display and polarization based, LC shutter based, or spectrallyselective based glasses to enable stereoscopic display. The mode may,for example, include one or more separate film-based backlightlightguide for 3D mode or a film-based lightguide and a displayconfigured to display images stereoscopically. The privacy mode, forexample, may include a switchable region of a polymer dispersed liquidcrystal disposed beneath a light redirecting element to increase ordecrease the viewing angle by switching to a substantially diffuse mode,or substantially clear mode, respectively. In another embodiment, thelight emitting device further includes a video display mode or a photodisplay mode wherein the color gamut is increased in the mode. In afurther embodiment, the light emitting device includes an alarm modewherein one or more lightguides is turned on to draw attention to aregion or a display. For example, when a cellphone is ringing, thelightguide that is formed around or on a portion of the exterior of thecellphone may be illuminated to “light up” the phone when it is ringing.By using a film-based lightguide, the lightguide film may be formed intoa phone housing (thermoforming for example) or it may be film-insertmolded to the interior (translucent or transparent housing) or exteriorof the housing. In another embodiment, the light emitting device has anemergency mode wherein at least one lightguide is illuminated to providenotification (such as displaying the illuminated word “EXIT”) orillumination (such as emergency lighting for a hallway). Theillumination in one or more modes may be a different color to provideincreased visibility through smoke (red for example).

NVIS Compatible Mode

The night vision or NVIS mode may include illuminating one or morelightguides, two or more light input couplers, or driving additionalLEDs at one or more light input couplers to produce the desiredluminance and spectral output. In this mode, the spectrum of the LEDsfor an NVIS mode may be compatible with US Military specificationsMIL-STD-3009, for example. In applications requiring an NVIS compatiblemode, a combination of LEDs or other light sources with different colorsmay be used to achieve the desired color and compatibility in a daytimemode and nighttime mode. For example, a daytime mode may incorporatewhite LEDs and blue LEDs, and a nighttime or NVIS mode may incorporatewhite, red, and blue LEDs where the relative output of one or more ofthe LEDs can be controlled. These white or colored LEDs may be disposedon the same light input coupler or different light input couplers, thesame lightguide or different lightguides, on the same side of thelightguide, or on a different side of the lightguide. Thus, eachlightguide may include a single color or a mixture of colors andfeedback mechanisms (such as photodiodes or LEDs used in reverse mode)may be used to control the relative output or compensate for colorvariation over time or background (ambient) lighting conditions. Thelight emitting device may further include an NVIS compatible filter tominimize undesired light output, such as a white film-based backlightlightguide with a multilayer dielectric NVIS compatible filter where thewhite lightguide is illuminated by white LEDs or white LEDs and RedLEDs. In a further embodiment, a backlight includes one or morelightguides illuminated by light from one or more LEDs of color selectedfrom the group: red, green, blue, warm white, cool white, yellow, andamber. In another embodiment, the aforementioned backlight furtherincludes a NVIS compatible filter disposed between the backlight orlightguide and a liquid crystal display.

Field Sequential Color Mode

In a further embodiment, a backlight or frontlight includes a lightguideincluding light extraction features and a light redirecting elementdisposed to receive a portion of the light extracted from the lightguideand direct a portion of this light into a predetermined angular range.In another embodiment, the light redirecting element substantiallycollimates, reduces the angular full-width at half maximum intensity to60 degrees, reduces the angular full-width at half maximum intensity to30 degrees, reduces the angular full-width at half maximum intensity to20 degrees, or reduces the angular full-width at half maximum intensityto 10 degrees, a portion of light from the lightguide and reduces thepercentage of cross-talk light from one light extraction region reachingan undesired neighboring pixel, sub-pixel, or color filter. When therelative positions of the light extraction features, light redirectingelements, and pixels, sub-pixels, or color filters are controlled thenlight from a predetermined light extraction feature can be controlledsuch that there is little leakage of light into a neighboring pixel,sub-pixel, or color filter. This can be useful in a backlight orfrontlight such as a color sequential backlight wherein threelightguides (one for red, green, and blue) extract light in a patternsuch that color filters are not needed (or color filters are includedand the color quality, contrast or gamut is increased) since the lightis substantially collimated and no light or a small percentage of lightextracted from the lightguide by a light extraction feature on the redlightguide beneath a pixel corresponding to a red pixel will be directedinto the neighboring blue pixel. In one embodiment, the light emittingdevice is a reflective display including a frontlight including threelightguides, each with a set of light extraction regions wherein thethree light extraction regions do not substantially overlap when viewedunder magnification looking from the viewing side of the display and thelight extraction regions substantially align with individual lightmodulating pixels on the light emitting display. In this embodiment,color filters are not required and the efficiency of the lightguides andlight emitting device can be increased. In one embodiment, eachlightguide includes a plurality of light extraction regions includingsubstantially one light extraction feature aligned substantially above alight modulating pixel in a reflective spatial light modulator. Inanother embodiment, each lightguide includes a plurality of lightextraction regions including a plurality of light extraction featureswith each light extraction region aligned substantially above a lightmodulating pixel in a reflective spatial light modulator. In oneembodiment, a light emitting display includes a reflective ortransmissive spatial light modulator and a film-based lightguideincluding an average of one or more selected from the group: 1, 2, 5,10, 20, 50, more than 1, more than 2, more than 5, more than 10, morethan 20, more than 20, and more than 50 light extraction features perspatial light modulating pixel when viewed normal to the light emittingsurface of the display.

In another embodiment, the light emitting device is a reflective displayincluding a reflective spatial light modulator and a frontlight orbacklight including three lightguides, each including a set of lightextraction regions wherein the uniformity of the light emitting from thefirst lightguide, second lightguide and third lightguide is greater thanone selected from the group: 60%, 70%, 80%, and 90% when illuminatedindividually. In this embodiment, the intensity of the light source(s)directing light into each lightguide may be modulated to providesequential color illumination for the reflective spatial lightmodulator.

Single or Multi-Color Mode

In one embodiment, the light emitting device includes a first lightguideand a second lightguide disposed to receive light in a lightguidecondition from a first light source and second light source,respectively, wherein the first light source has a color differenceΔu′v′ greater than 0.004 from the second light source. In anotherembodiment, the light emitting device includes a three lightguidesdisposed to receive light in a lightguide condition from three lightsources wherein the three light sources each have a color differenceΔu′v′ greater than 0.004. For example, in one embodiment, a reflectivedisplay includes a frontlight including a first, second, and thirdlightguide disposed to receive light from a red, green, and blue LED andeach lightguide emits light toward the reflective spatial lightmodulator where it is modulated spatially and when driven with allpixels in the “on” or reflective mode, the spatial luminance uniformityof the light emitting pattern from each lightguide individually isgreater than one selected from the group: 60%, 70%, 80%, and 90%.

Multi-Color or Full-Color Display

In one embodiment, the light emitting device includes at least onemonochromatic light source (such as a red light emitting diode) and awhite light source (such as a white light emitting diode). In anotherembodiment, the light emitting device includes a light emitting regionwith a first color light emitting region emitting light from a firstlight source and a second color light emitting region emitting lightfrom a second light source. In one embodiment, the first color lightemitting region is spatially separate from the second color lightemitting region. For example, in one embodiment, the light emittingdevice is a display including a monochrome (first color) display areaused for icons or buttons within or adjacent a display area and afull-color display area for viewing full-color content. In a furtherembodiment, the first color light emitting region overlaps at least aportion of the second color light emitting region. For example, in oneembodiment, the light emitting device is a display including a firstcolor light emitting region used for icons or buttons within or adjacenta display area and a second color light emitting display area forviewing of full-color content. In this embodiment, the first color lightemitting area can be illuminated by monochrome light (in a low powermode for example) or full-color light (in a higher color gamut mode, forexample). In another embodiment, the first color light emitting regionoverlaps the second color light emitting region. For example, in oneembodiment, the light emitting device includes a display with a lightemitting region including a white illumination lightguide configured toreceive light from at least one white LED, where the white illuminationlightguide is above or below a full-color illumination lightguidedisposed to receive light from at least one red, green, and blue LED. Inthis embodiment, the display can be operated in a high brightness, lowcolor saturation mode by turning one or more white LEDs forillumination, or the display can be operated in a high color saturation,reduced brightness mode. In one embodiment, two or more light sourceswith different colors (such as white, red, green, and blue) arepositioned to illuminate the same light input surface of a stack ofcoupling lightguides such that the light emitted from the light emittingarea can be a first color mode (white only, for example), ormulti-colored mode (red, green, and blue mode, for example). In thisembodiment, for example, the display can be illuminated from a singlefilm-based lightguide, and the display can be driven in a monochromemode, a full color high saturation mode using light from red, green, andblue LEDs, or a lower saturation full-color, higher brightness modeusing red, green, blue, and white LEDs.

In one embodiment, the display includes color filters. In oneembodiment, a display including color filters has a first color gamutwhen illuminated by white light source (such as a white light emittingLED including a Yttrium Aluminum Garnet (YAG) phosphor with a correlatedcolor temperature between 3700K and 4000K) and has a second color gamut,different from the first color gamut, when illuminated by one or moremonochrome light source (such as a red, green, and blue LEDs). In oneembodiment, the first color gamut is one selected from the group: lessthan 60%, less than 70%, less than 80%, less than 90%, less than 100%,greater than 60%, greater than 70%, greater than 80%, greater than 90%,and greater than 100% of the National Television System Committee (NTSC)color gamut, and the second color gamut is one selected from the group:less than 70%, less than 80%, less than 90%, less than 100%, greaterthan 70%, greater than 80%, greater than 90%, greater than 100%, greaterthan 110%, and greater than 120% of the National Television SystemCommittee (NTSC) color gamut.

In one embodiment, the light emitting device monitors the intensity orcolor of one or more light sources directly or indirectly. In anotherembodiment, the light emitting device monitors the intensity or color ofthe light emitting region. The intensity or color can be monitored inreal-time using a photodetector, such as, for example, a photodiode,photocell, or light emitting diode used in reverse mode to detect lightwithin a specific wavelength band. In one embodiment, the light emittingdevice monitors the color and/or intensity to adjust for ambient lightconditions or degradation of a component. For example, in oneembodiment, the light emitting device includes a light emitting diodepositioned to receive light from a plurality of light sources and whenthe light output reduces over time, the current is increased such thatthe light output remains substantially the same. In another embodiment,the relative light output of two light sources, such as a red and blueLED are monitored such that the relative light output can be maintainedand the color remains substantially the same. In this embodiment, thelight emitting device can include multiple lightguides illuminated bymultiple monochrome light sources such that the light emitting device isin a color sequential mode. In another embodiment, the light emittingdevice monitors the light after it passes through the lightguide region.In one embodiment, the light emitting device includes a first lightinput coupler positioned to receive light from a first light source anda second light input coupler positioned to receive light from a secondlight source. In this embodiment, the light passing through thelightguide region is monitored by measuring the relative intensity oflight passing through the first array of coupling lightguides in thefirst light input coupler, the lightguide region, and the second arrayof coupling lightguides in the second light input coupler to the secondarray of LEDs that also includes at least one LED driven in reverse modeto detect intensity of the light exiting the coupling lightguides at thelight input surface. In this embodiment, the degradation of thelightguide or one or more components of the lightguide or optical systemcan be monitored for degradation such as yellowing due to UV exposureand the relative output of the light source could be increased(increasing the light output from the blue LED to maintain the color,for example). In one embodiment, one or more light sources in a firstinput coupler are turned on while the light sources in the second inputcoupler are turned off such that a photodiode or light emitting diode inthe second light input coupler can measure the light from the one ormore light sources in the first input coupler that travels through theinput couplers and lightguide. This could be performed in a testing modebefore, during, or the display is turned on or in a viewing mode. In oneembodiment, the light transmitting material of the core and/or claddingregion of the film-based lightguide has an absorption coefficient, alpha(absorption), greater than one selected from the group: 0.01, 0.02,0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,0.7, and 0.8 per inch. In one embodiment, the light transmittingmaterial of the core and/or cladding region of the film-based lightguidehas an attenuation coefficient, alpha (attenuation), accounting forabsorption and scatter greater than one selected from the group: 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, and 0.8 per inch. The attenuation or absorption coefficientcan be measured by sequentially measuring the light output from a lengthof lightguide material by cutting the material and fitting the data tothe curve model analogous to the “cutback” method for evaluatingattenuation in optical fibers.

In one embodiment, the intensity of light from a first light source of afirst monochrome color is increased in order to adjust for theabsorption and/or attenuation loss within the light transmittingmaterial within the wavelength range. For example, in one embodiment, alight emitting device includes at least one red, green, and blue LEDlight sources, the light transmitting material of the core layer of thelightguide absorbs more blue light than red light, and the intensity oflight from the blue light emitting diode is at least a first intensityadjustment percentage more than the intensity required to meet at least70%, 80%, or 90% of the NTSC color gamut at a specific luminance (suchas 50, 100, 200, or 300 candelas/m²) if the light was not absorbed orattenuated by the light transmitting material in the film-basedlightguide. This comparison can be made by measuring the color gamut ofthe light from the red, green, and blue LEDs directly (without passingthrough the lightguide) and the light that exits the light emitting areaof the film-based lightguide. For example, in one embodiment, in orderto meet an 80% NTSC color gamut in the light emitting area of thedisplay at 300 candelas/m², the intensity of the light from the blue LEDis increased by a first intensity adjustment percentage of 20% over theintensity that would be required to reach the 80% NTSC color gamut dueto direct illumination from the LEDs without using the film-basedlightguide. In one embodiment, the first intensity adjustment percentageis greater than one selected from the group: 5%, 10%, 20%, 30%, 40%,50%, 60%, 70%, 80%, 90%, and 100%.

In one embodiment, the array of color filters includes one or more colorfilters selected from the colors: red, green, blue, cyan, magenta,yellow, orange, and violet. In one embodiment, the light emitting deviceis a color display including at least one color filter with a firstwavelength transmission bandwidth with a transmission greater than 60%at normal incidence and at least one light source with a peak wavelengthoutput within the first wavelength transmission bandwidth. In anotherembodiment, the light emitting device is a display including an array ofcolor filters including a first color filter, second color filter, andthird color filter with first, second and third wavelength bandwidths,respectively. In this embodiment, the display further includes a first,second and third light sources emitting light within the first, second,and third wavelength bandwidths, respectively, or emitting light with apeak intensity within the first, second, and third wavelengthbandwidths, respectively.

In one embodiment, the light emitting device includes one or moremonochrome light sources and the light extraction features arediffractive in nature. For example, in one embodiment, the lightextraction features are diffractive elements positioned to diffractincident light out of the lightguide directly (by transmission) orindirectly (by reflection such that the light exits the lightguide onthe side of the lightguide opposite the diffractive elements). In oneembodiment, the diffractive elements include linear blazed gratings. Inone embodiment, the light emitting device includes a lightguide withfirst diffractive element light extraction features and seconddiffractive element light extraction features different than the firstdiffractive element light extraction features, a first light sourceemitting light with a first peak wavelength, a second light sourceemitting light with a second peak wavelength different from than thefirst peak wavelength, wherein the first diffractive element lightextraction features diffract light from the first light source out ofthe lightguide (directly or indirectly from the opposite side) and donot diffract incident light from the second light source out of thelightguide (directly or indirectly). In a further embodiment, the seconddiffractive element light extraction features diffract light from thesecond light source out of the lightguide (directly or indirectly fromthe opposite side) and do not diffract incident light from the firstlight source out of the lightguide (directly or indirectly). In anotherembodiment, the light incident upon the diffractive element lightextraction features within the lightguide has an angular full width athalf maximum intensity within the lightguide less than one selected fromthe group: 100, 90, 80, 70, 60, 50, 40, 30, 20, and 10 degrees in one ormore illumination planes.

Automatic or User Controlled Color Adjustment

In one embodiment, the light emitting device can be operated in amonochrome mode (such as blue-only mode). In another embodiment, theuser of the light emitting device can selectively choose the color ofthe light emitted from the display or light emitting device. In anotherembodiment, the user can choose to change the mode and relative lightoutput intensities from one or more light sources. For example, in oneembodiment, the user can switch from a full-color 2D display using onlythe frontlight to a stereoscopic 3D display mode. In one embodiment, theuser can adjust the color temperature of the white point of the displayincluding a film-based lightguide and a light input coupler disposed tocouple light from a red LED and a white LED into the couplinglightguides of the lightguide by adjusting the light output of the redLED relative to the white LED. In another embodiment, the user canswitch a reflective display from a fixed white point color temperaturefrontlight only mode to an automatic white color temperature adjustmentfrontlight and ambient light mode that automatically adjusts the lightoutput from a red LED relative to a white LED (or the relativeintensities of blue, green, and red LEDs, etc.) to maintain the colortemperature of the white point of the display in a variety ofenvironmental ambient light spectral conditions such as “cool”fluorescent lighting and “warm” lighting from an incandescent bulb. Inanother embodiment, the user can select to change from a full-color RGBdisplay mode to an NVIS compatible display mode with less red lightoutput. In another embodiment, the user can select to change from an RGBillumination with light from red, green, and blue LEDs to a monochromemode with light from white LEDs.

In a further embodiment, a film-based lightguide is disposed to receivelight from a substantially white light source and a red light source.For example, by coupling light from a white LED and a red LED, the colortemperature of the display can be adjusted. This can, for example, bechanged by the user (for color preference, for example) orautomatically. For example, in one embodiment, a light emitting deviceincludes a reflective display and a photosensor (such as one or morephotodiodes with color filters or LEDs operated in reverse) that detectsthe color or spectral intensity of light within one or more wavelengthbandwidths and adjusts the overall and/or relative light outputintensities of the frontlights (or LEDs disposed to couple light into asingle frontlight) to increase or decrease the luminance and/or adjustthe combined color of light emitted from the reflective display. Inanother embodiment the light detector (or photosensor) used to detectthe color or spectral intensity of light within one or more wavelengthbandwidths also determines the relative brightness of the ambient lightand the intensity of the light from the frontlight is increased ordecreased based on predetermined or user adjusted settings. In oneembodiment, the photosensor includes one or more light sensors such asLEDs used in reverse mode. In one embodiment, the photosensor isdisposed in one or more locations selected from the group: behind thedisplay, behind the frontlight, between the light emitting region of thedisplay and the bevel, bezel or frame of the display, within the frameof the display, behind the housing or a light transmitting window of thehousing or casing of the display or light emitting device, and in aregion of the light emitting device separate from the display region. Inanother embodiment, the photosensor includes a red, green, and blue LEDdriven in reverse to detect the relative intensities of the red, green,and blue spectral components of the ambient light. In anotherembodiment, the photosensor is disposed at the input surface of anarrangement of coupling lightguides disposed to transmit light from oneor more light sources to the light emitting region of a film-basedlightguide or at the output surface of output coupling lightguidesextending from the film-based lightguide. In this embodiment, thephotosensor can effectively collect the average intensity of the lightincident on the display and the film-based lightguide frontlight andthis can be compared to the relative output of the light from the lightsources in the device. In this embodiment, the photosensor is lesssusceptible to shadows since the area of light collection is larger dueto the larger spatial area including the light extraction features thatare effectively working in reverse mode as light input coupling featurescoupling a portion of ambient light into the lightguide in a waveguidecondition toward the photosensor.

One or more modes of the light emitting device may be configured to turnon automatically in response to an event. Events may be user oriented,such as turning on the high color gamut mode when the cellphone is usedin the video mode, or in response to an environmental condition such asa film-based emergency light fixture electrically coupled to a smokedetection system (internal or external to the device) to turn on whensmoke is detected, or a high brightness display mode automaticallyturning on when high ambient light levels are detected.

In another embodiment, the display mode may be changed from a lowerluminance, higher color gamut mode (such as a mode using red, green, andblue LEDs for display illumination) to a higher luminance, lower colorgamut mode (such as using white LEDs for illumination). In anotherembodiment, the display may switch (automatically or by user controls)from a higher color gamut mode (such as a light emitting device emittinglight from red, green, and blue LEDs) to a lower color gamut mode (suchas one using white phosphor based LEDs). In another embodiment, thedisplay switches automatically or by user controls from a highelectrical power mode (such as light emitting device emitting light fromred, green, and blue LEDs) to a relatively low electrical power mode(such as a mode using only substantially white LEDs) for equal displayluminances.

In a further embodiment, the display switches automatically or by usercontrols from a color sequential or field sequential color modefrontlight or backlight illumination mode to an ambient-lightillumination mode that turns off or substantially reduces the lightoutput from the frontlight or backlight and ambient light contributes tomore than 50% of the flux exiting the display.

In one embodiment, a display includes a film-based lightguide with alight input coupler disposed to receive light from one or more lightsources emitting light with one or more colors selected from the group:a red, green, blue, cyan, magenta, and yellow. For example, in oneembodiment, a display includes a film-based lightguide including one ormore light input couplers disposed to receive light from a red, green,blue, cyan and yellow LED. In this embodiment, the color gamut of thedisplay can be increased significantly over a display including onlyred, green, and blue illumination LEDs. In one embodiment, the LEDs aredisposed within one light input coupler. In another embodiment, two ormore LEDs of two different colors are disposed to input light into anarrangement of coupling lightguides. In another embodiment, a firstlight input coupler includes one or more LEDs with a first spectraloutput profile of light entering a film-based lightguide and a secondlight input coupler with a second spectral output profile of lightentering the film-based lightguide different than the first spectraloutput profile and the coupling lightguides in the first or second lightinput coupler are disposed to receive light at the input surface from anLED with a first peak wavelength and output wavelength bandwidth lessthan 100 nm and the coupling lightguides in the other light inputcoupler are not disposed to receive light at the input surface from anLED with substantially similar peak wavelength and substantially similaroutput wavelength bandwidth. In another embodiment, a light emittingdevice includes two or more light input couplers including differentconfigurations of different colored LEDs. In another embodiment, a lightemitting device includes two or more light input couplers includingsubstantially the same configurations of different colored LEDs.

Stereoscopic Display Mode

In another embodiment, a display capable of operating in stereoscopicdisplay mode includes a backlight or frontlight wherein at least onelightguide or light extracting region is disposed within or on top of afilm-based lightguide wherein at least two sets of light emittingregions can be separately controlled to produce at least two sets ofimages in conjunction with a stereoscopic display. The 3D display mayfurther include light redirecting elements, parallax barriers,lenticular elements, or other optical components to effectively convertthe spatially separated light regions into angularly separated lightregions either before or after spatially modulating the light.

In a further embodiment, a light emitting device includes at least onefirst lightguide emitting light in a first angular range and at leastone second lightguide emitting light in a second angular range. Byemploying lightguides emitting lightguides emitting light into twodifferent angular ranges, viewing angle dependent properties such asdual view display or stereoscopic display or backlight can be created.In one embodiment, the first lightguide emits light with an optical axissubstantially near +45 degrees from the normal to the light outputsurface and the second lightguide emits light with an optical axissubstantially near −45 degrees from the normal to the light outputsurface. For example, a display used in an automobile display dashbetween the driver and passenger may display different information toeach person, or the display may more efficiently direct light toward thetwo viewers and not waste light by directing it out normal to thesurface. In a further embodiment, the first lightguide emits lightcorresponding to light illuminating first regions of a display (or afirst time period of the display) corresponding to a left image and thesecond lightguide emits light corresponding to light illuminating secondregions of a display (or a second time period of the display)corresponding to a right image such that the display is a stereoscopic3D display.

In one embodiment, the first lightguide emits substantially white lightin a first angular direction from a first set of light extractionfeatures and a second light guide beneath the first lightguide emitssubstantially white light in a second angular direction from a secondset of light extraction features. In another embodiment, the first setof light extraction features are disposed beneath a first set of pixelscorresponding to a left display image and the second set of lightextraction features are substantially spatially separated from the firstand disposed beneath a second set of pixels corresponding to a rightdisplay image and the display is autostereoscopic. In a furtherembodiment, the aforementioned autostereoscopic display further includesa third lightguide emitting light toward the first and second sets ofpixels and is illuminated in a 2D display mode display full resolution.

In one embodiment, a light emitting display includes a film-basedlightguide and a reflective spatial light modulator wherein the lightreflected by the reflective spatial light modulator from light incidentfrom a lightguide due to light extracted from the lightguide propagatingin a first direction does not substantially overlap the light reflectedby the reflective spatial light modulator from light incident from thelightguide extracted from light propagating in a second directiondifferent from the first direction. In one embodiment, a light emittingdisplay includes a reflective spatial light modulator with a diffuselyreflecting properties wherein the angular full-width at half maximumintensity of the diffusely reflected light is less than one selectedfrom the group: 50 degrees, 40 degrees, 30 degrees, 20 degrees, and 10degrees when measured with laser light with a divergence less than 3milliradians at an incidence angle of 35 degrees. In one embodiment, thediffusely reflecting spatial light modulator receives light from twopeak directions from light exiting a film-based lightguide propagatingwithin the lightguide with optical axes substantially oriented inopposite directions. For example, in this embodiment, light propagatingin a first direction within a lightguide can be extracted from thelightguide such that it is incident on the reflective spatial lightmodulator at an angle of peak luminous intensity of +20 degrees from thenormal to the reflective spatial light modulator with an angularfull-width at half maximum intensity of 10 degrees in a first outputplane and light propagating in a second direction opposite the firstdirection within a lightguide can be extracted from the lightguide suchthat it is incident on the reflective spatial light modulator at anangle of peak luminous intensity of −20 degrees from the normal to thereflective spatial light modulator with an angular full-width at halfmaximum intensity of 10 degrees in the first output plane. In thisembodiment, the light originally propagating in the lightguide in thefirst direction is output at an angle of peak luminous intensity ofabout −20 degrees from the display normal and light originallypropagating in the lightguide in the second direction is output from thedisplay at an angle of about +20 degrees from the display normal in thefirst output plane. By modulating the light output (such as alternatinglight from two white LEDs coupled into two input coupling lightguides onopposite sides of a light emitting region), and synchronizing this withthe reflective spatial light modulator, alternating images from thedisplay can be directed into the +20 and −20 degree directions such thatthe viewer sees a stereoscopic 3D image, indicia, graphics, or video. Inanother embodiment, the angle of peak intensity of the light from thefirst and second directions varies across the frontlight such that thelight is focused toward two “eye boxes” corresponding to a range ofviewing positions for an average viewer's eyes at a particular viewingdistance. In one embodiment, the angle of peak luminous intensity at thecenter of the display from the light originally propagating with itsoptical axis in a first direction within a film-based lightguide iswithin a range selected from the group: −40 degrees to −30 degrees, −30degrees to −20 degrees, −20 degrees to −10 degrees, and −10 degrees to−5 degrees from the normal to the display surface in a first outputplane and the angle of peak luminous intensity at the center of thedisplay from the light originally propagating with its optical axis inthe film-based lightguide in a second direction is within a rangeselected from the group: +40 degrees to +30 degrees, +30 degrees to +20degrees, +20 degrees to +10 degrees, and +10 degrees to +5 degrees fromthe normal to the display surface in the first output plane. In anotherembodiment, the first output plane is substantially parallel to thefirst and second directions.

In one embodiment, a light emitting display includes a lenticular lensdisposed to direct light into two or more viewing zones for stereoscopicdisplay of images, video, information, or indicia and the lenticularlens is a film-based lightguide or includes a film-based lightguidesubstrate. In this embodiment, the thickness of the stereoscopic displaycan be reduced by incorporating the film-based lightguide into thelenticular lens film. In a further embodiment, stray light reflectionsfrom frontlight at the air-lenticule surfaces are reduced by directinglight from the lenticular lens toward the reflective display withoutpassing through the lenticule-air surface until after reflection fromthe reflective spatial light modulator.

Aligned Extraction Features

In one embodiment, the arrangement of light extraction features isaligned with one or more color filters, such as the color filters in anarray of color filters. In one embodiment, the arrangement of lightextraction features are aligned and positioned within an illuminationvolume defined by the lateral edges of the color filters in an array ofcolor filters or spatial light modulating pixels and the thickness ofthe light emitting device in a direction normal to the light emittingarea surface. In another embodiment, the arrangement of light extractionfeatures are aligned and positioned within an illumination volumedefined by the lateral edges of the color filters in the array of colorfilters or the spatial light modulating pixels and a direction parallelto the angle of peak intensity of light exiting the lightguide from thelight extraction features. For example, in one embodiment, a lightemitting display includes a film-based frontlight emitting light into acladding or air region from light extraction features with an angle ofpeak intensity of 60 degrees from the normal to the light emitting areasurface in air or the cladding and the arrangement of light extractionfeatures are within the illumination volume defined by the lateral edges(parallel to the surface of the film) of the color filters in the arrayof color filters and extending at an angle (above or below thelightguide) of 60 degrees from the light exiting the lightguide wherethe angle is measured within the cladding (or air if air is thecladding) or within a component or substrate of a component adjacent thecore region. In one embodiment, more than one percentage selected fromthe group: 50%, 60%, 70%, 80%, 90%, and 95% of the light extractionfeatures are aligned and positioned within the illumination volumedefined by the lateral edges of the color filters in the array of colorfilters or spatial light modulating pixels, and a direction normal tothe light emitting area surface or a direction parallel to the angle ofpeak intensity of the light exiting the lightguide region due to thelight extraction features. In another embodiment, less than one selectedfrom the group of 50%, 40%, 30%, 20%, 10% and 5% of the light extractionfeatures are positioned within the volume defined outside of the lateraledges of the color filters in an array of color filters or spatial lightmodulating pixels, and the direction normal to the light emitting areasurface or the direction parallel to the angle of peak intensity of thelight exiting the lightguide region. In one embodiment, the lightextraction features are positioned such that the percentage of lightexiting the lightguide in the light emitting area corresponding to theactive area of the display that reaches the light transmitting colorfilters in the array of color filters or the light modulating regions ofthe display pixels is greater than the fill factor percentage of thearray of color filters or the array of spatial light modulating pixels,respectively. In a further embodiment, the light extraction features arepositioned such that a visible Moiré pattern is not introduced into thesystem due to the arrangement of light extraction features, colorfilters and/or pixels. Moiré patterns and methods for avoiding orreducing their visibility are known in the display industry and aredetailed, for example in U.S. Pat. Nos. 6,333,817 and 5,684,550, thecontents of which are incorporated by reference herein. In anotherembodiment, the illumination volume includes an average of one lightextraction feature per color filter or pixel. In another embodiment, theillumination volume includes at least an average of one selected fromthe group: 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, and 30 light extractionfeatures per color filter in an array of color filters or spatial lightmodulating pixel in a spatial array of light modulating pixels.

Other Devices

In one embodiment, the film-based lightguide illuminates a display,phase modulating device, component of an optical communication device,component of a medical device, or component of an analytical device. Inanother embodiment, a device comprises the film-based lightguide and theone or more light sources emit light with a constant phase wavefront,uniform phase wavefront, predetermined phase wavefront, compensatedphase wavefront, or adjustable phase wavefront across the area or at oneor more sub-regions of the light input surface area of the light inputcoupler for the film-based lightguide. In one or more embodiments, thelight exiting the light emitting area of the light emitting devicereflects from a spatial modulation device (phase and/or amplitude) ortransmits through a spatial modulation device (phase and/or amplitude)and may or may not pass back through one or more regions of thelightguide (such as the light emitting area). If the light from themodulating device passes back through the lightguide, the modulatingelement may pre-compensate for the phase or amplitude change due topassing through the lightguide to result in a predetermined phase oramplitude output (such as a uniform constant phase wavefront, forexample).

Optical Tweezers

In one embodiment, a device that provides an attractive or repulsiveforce on one or more microscopic (or smaller scale) dielectric objectsfor trapping or manipulation, such as optical tweezers, comprises thefilm-based lightguide, wherein the light output from the light emittingarea provides illumination to a phase modulating element (or amplitudemodulating element). In this embodiment, the light output from the lightemitting area of the lightguide can have one or more selected from thegroup: constant phase wavefront, uniform phase wavefront, predeterminedphase wavefront, compensated phase wavefront, or adjustable phasewavefront across the area or spatially varying across the light emittingarea. For example, in one embodiment, the light from the light emittingarea of the film-based lightguide is incident on a Liquid Crystal OnSilicon (LCOS) phase modulation device that compensates for the phasevariation to produce a predetermined phase across the cross-sectionalarea of the reflected light from the LCOS device that is directed towarda material comprising at least one dielectric object. In this example,the spatially modulating the phase of the LCOS device can compensate forthe phase variation received from the output from the light emittingarea of the lightguide and further modulate the phase to produce aspatially varying phase wavefront that can be used to apply anattractive force, repulsive force or to trap one or more dielectricobjects. In another embodiment, the spatial light modulator adjusts thelight input into the input surface of the light input coupler such thatthe light output from the light emitting area of the film-basedlightguide has a uniform, predetermined, constant, varying, or otherwisecontrolled phase and/or light output. In this embodiment, for example, areflective LCOS spatial light modulator can receive light and alter thephase of the light reflecting from the reflective LCOS such that thelight having passed through the film-based lightguide can have apredetermined phase and/or amplitude at the output from the lightemitting area. In this example, the reflective LCOS could be used toeffectively pre-compensate for any phase or amplitude variation of thelight traveling through the film-based lightguide (and optionallycompensate for variation due to the light output from the light emittingarea reflecting off of a surface or sample and passing back through thefilm-based lightguide). In one embodiment, an imager is used to viewreflected light received or transmitted from the light emitting area toadjust the spatial phase and/or amplitude of the light from the lightemitting area of the lightguide to provide a calibration (such as bygenerating a uniform set of interference fringes, a constant intensity,a constant phase, or a uniform interference pattern, for example).

Spatially Varying Display

In one embodiment, a display device comprises the film-based lightguide,wherein the light output from the light emitting area providesillumination to an amplitude or phase spatial light modulator. In thisembodiment, the light output from the light emitting area of thelightguide can have one or more selected from the group: constant phasewavefront, uniform phase wavefront, predetermined phase wavefront,random phase wavefront, compensated phase wavefront, or adjustable phasewavefront across the area or spatially varying across the light emittingarea. For example, in one embodiment, the light emitting area emitslight that is directed onto a Liquid Crystal On Silicon (LCOS) phasemodulation device. The LCOS device may spatially modulate the phase ofthe light reflecting from the modulating device to create diffractionpatterns that form a near-field or far-field spatial image, phasewavefront, or amplitude wavefront. By illuminating the spatial lightmodulator (phase or amplitude modulator) with light from light sourceswith different peak luminous intensity wavelengths (such as red, green,and blue LEDs, or red, green, and blue lasers), the light transmittedthrough or reflected from the spatial light modulator can form afar-field image, video, or phase wavefront. In this embodiment, thelight from the light sources with different peak intensities may bedirected through the same input coupler, different input couplers on thesame film, or on input couplers on multiple film-based lightguides.Light sources emitting light with wavelengths outside of the visiblespectrum, such as infra-red or ultraviolet wavelengths, may be used toprovide a display for a particular application such as a night-visioncompatible display or a wavelength conversion display comprising one ormore fluorophores, phosphors, quantum dots, up-converting materials, orother materials that convert light with a first spectral range ofwavelengths to a second spectral range of wavelengths different than thefirst spectral range of wavelengths.

By spatially modulating the phase of the light from the LCOS device, onecan compensate for the phase (or amplitude) variation received from theoutput from the light emitting area of the lightguide and furthermodulate the phase (or amplitude) to produce a spatially varying phase(or amplitude) wavefront. In one embodiment, the display is ahead-mounted display, head-up display (such as used in a vehicle oraircraft), projection display, pico projector, near-eye display, wedgeprojection display, digital holography display, direct view display,virtual display, microlens array based integral display, or lightfielddisplay. In one embodiment, a spatial light modulator is positioned tospatially modulate (amplitude or phase) the light before entering intothe light input surface of the light input coupler of the light emittingdevice, wherein the modulated light propagates through the light mixingregion to the light emitting region and is emitted from the lightemitting area in the form of a two-dimensional array of light emittinglocations. In this embodiment, the light from the light emitting areamay form a direct view display, a virtual display, or a lightfielddisplay. The light may be directed from the light emitting area of thelightguide using one or more selected from the group: light extractionfeatures, light redirecting features, low angle directing features,light turning features, high refractive index regions or layers, lowrefractive index regions or layers, and light redirecting opticalelements.

In another embodiment, a spatial light modulator is positioned tospatially modulate (amplitude or phase) the light received from thelight emitting area of the film-based lightguide, wherein the modulatedlight may pass through the spatial light modulator (transmissive spatiallight modulator) or reflect from the spatial light modulator (reflectivespatial light modulator). For reflective spatial light modulators, thefilm-based lightguide may be positioned such that light spatiallymodulated and reflected from the spatial light modulator passes backthrough the film-based lightguide (such as passing back through thelight emitting region of the film-based lightguide).

Head-Mounted Display (HMD)

In one embodiment, a head-mounted display (HMD) comprises the film-basedlightguide, wherein the light output from the light emitting areaprovides illumination to an amplitude or phase spatial light modulator.In one embodiment, the light from the light emitting region providesillumination to the amplitude or phase spatial light modulator as afrontlight or a backlight. In another embodiment, the spatiallymodulated light from the amplitude or phase spatial light modulator isdirected onto the input surface of a light input coupler, propagatesthrough the lightguide film, and is emitted from the lightguide anddirected to one or more eyes of the viewer wearing the head-mounteddisplay. In one embodiment, an eyewear frame or one or more arms of aframe comprises one or more selected from the group: the light mixingregion of the lightguide, an inactive region of the lightguide, thespatial light modulator, the light source, and the electronics. In oneembodiment, the light emitting area of the film-based lightguide ispositioned on a surface or within a lens of eyewear. In anotherembodiment, the head-mounted display is an attachment that can bepermanently or removably attached to eyewear such as sunglasses orprescription eyewear. In this embodiment, the light emitting area may bea film that can be pressed, laminated, glued, placed adjacent,physically coupled, or optically coupled to or adjacent a lens or frameof eyewear. In one embodiment, the array of coupling lightguides extendover one selected from the group: 5, 10, 15, 20, 30, 40, 50, 60, and 70percent of the length of the frame along one side of the eyewear. Inanother embodiment, the light mixing region of the lightguide extendsover one selected from the group: 5, 10, 15, 20, 30, 40, 50, 60, and 70percent of the length of the frame along one side of the eyewear.

Head-Up Display (HUD),

In one embodiment, a Head-Up Display (HUD) system comprises thefilm-based lightguide, wherein the light output from the light emittingarea provides illumination to an amplitude or phase spatial lightmodulator. In one embodiment, the light emitting area of the film-basedlightguide is positioned on a surface or within a window or lighttransmitting substrate. A Head-Up Display comprising a film-basedlightguide can be configured to be substantially transparent when notdisplaying information or images and/or substantially transparent inportions of the light emitting region that are not emitting light basedon the image being display. In another embodiment, the HUD is anattachment that can be permanently or removably attached to a window ormirror of an automobile, vehicle, or aircraft. In this embodiment, thelight emitting area may be a film that can be pressed, laminated, glued,placed adjacent, physically coupled, or optically coupled to or adjacenta window, substrate, lens or light transmitting material.

Wedge Projection Display

In one embodiment, a wedge projection display system comprises thefilm-based lightguide, wherein the light output from the light emittingarea provides illumination to an amplitude or phase spatial lightmodulator. In another embodiment, a wedge projection display comprises afilm-based lightguide wherein the light input surface of the light inputcoupler receives light from a spatial light modulator (amplitude and/orphase modulated light) and the light received by the light input surfacepropagates through a light mixing region of the lightguide and into alight emitting region of the lightguide. In one embodiment, the wedgeprojection display comprises a film-based lightguide wherein thethickness of film (or lightguide region of a film) decreases within thelight emitting region in the average direction of propagation of thelight within the lightguide region of the film, in a direction away fromthe side where light enters the light emitting region to the oppositeside of the light emitting region, or along the direction of propagationof the light traveling within the light emitting region. In thisembodiment, the wedge shape of the lightguide extracts light (such aslight collimated to an angular FWHM of less than 5 degrees, for example)propagating within the lightguide region of the film by graduallydecreasing the angle of propagation (relative to the surface normal)such that it escapes the lightguide in a particular area of the lightemitting region. In one embodiment, a wedge, prism, or angularlydirecting optical element is positioned between the spatial lightmodulator and the light input surface of the light input coupler todirect collimated light to an angle less than 90 degrees from thestacked surfaces of the coupling lightguides stacked to form the lightinput surface. In another embodiment, the light input surface has anaverage angle greater than 0 degrees from the thickness direction of thestacked coupling lightguides. In one embodiment, the light input to orfrom the spatial light modulator is collimated to an angular FWHM lessthan one selected from the group of 20, 10, 5, 4, 3, 2, 1, and 0.5degrees in one or more planes such as two orthogonal planes of incidenceor the plane comprising the thickness direction of the film. In anotherembodiment, a first film-based lightguide provides collimated light tothe spatial light modulator and a second film-based lightguide receivesthe spatially modulated light from the spatial light modulator through asecond light input surface of a second light input coupler, the lightpropagating through a second array of coupling lightguides and into atapered light emitting region of the lightguide. In another embodiment,the light emitting region comprises a plurality of low angle redirectionfeatures (such as surface modification or optically coupling a film withsurface relief features) that decrease the angle of propagation(relative to the thickness direction) of the light in the light emittingregion of the lightguide. In this embodiment, a single wedge or taperedlightguide may be replaced by a plurality (such as an array orarrangement) of low angle redirecting features that decrease the angleof propagation (relative to the surface normal) of the light propagatingin the light emitting region to extract light from the core orlightguide region of the lightguide in the light emitting region. Inthis embodiment, for example, low angle redirection features mayspatially direct light to light extraction features or light turningfeatures.

In another embodiment, an array of passive or active light redirectingelements (such as an array prismatic features arranged in columns witheach column comprising a different features with different prism anglesfrom adjacent columns) is positioned between the spatial light modulatorand the light input surface of the light input coupler of the film-basedlightguide and spatially changes the angle of the light in differentspatial areas reaching the light input surface. For example, the angleof the light from each column of pixels (or groups of columns of pixels)of the spatial light modulator (or the angle of light reaching each ofthe column of pixels) may be changed spatially when the columns ofpixels are oriented in a direction parallel to the stack direction ofthe stacked coupling lightguides, and one or more rows of the spatiallight modulator are positioned such that light from the one or more rowsof pixels enters a single coupling lightguide of the array of couplinglightguides. In this embodiment, the light from the one or more rows ofpixels correspond to a single coupling lightguide and within thecoupling lightguide, different columns of pixels are directed intodifferent angles of propagation within the lightguide in a planecomprising the thickness direction of the film. In this embodiment, thelow angle light direction features (or a wedge or tapered lightguide inthe light emitting region) may progressively couple light out of thecore region of the lightguide from different columns as the light fromeach coupling lightguide travels within a region corresponding to a rowof display pixels parallel to the direction of taper or low angle lightredirection in the light emitting area. The array of light redirectingelements may be an array of prisms wherein the angle of each column ofprism features in the array of prisms varies slightly (increasing) alongthe columns. Thus refracting the light from the columns into slightlydifferent angles.

In this embodiment, the collimated light incident on the spatial lightmodulator propagates to the light emitting region of the lightguide withthe light beam redirected from each prism remaining collimated, whereinthe strips correspond to one or more rows of the spatial display of thelight emitting region and different angles of light within each strip ina plane comprising the thickness direction correspond to the differentcolumns of light output of the spatial display of the light emittingregion.

In another embodiment, the array of light redirecting elements is anactive optical element such as liquid crystal modulator, an array ofmicrofluidic optical elements, MEMS array, or other active opticalelement that can change the angle of incident light to a chosen secondangle of light different from the first angle such that the final angleof light within the light emitting region of the lightguide can becontrolled to achieve light redirection at the desired lateral locationcorresponding to a column in a display. In this embodiment, the angle ofthe light entering into the light input coupler for each pixel may bepre-adjusted such that the light is extracted in the light emittingregion at the appropriate column and/or row to form the spatial array oflight emitting pixels.

In another embodiment, a spatial light modulator that spatiallyredirects the angle of light into different directions may be used toprovide the light redirection for output coupling and to modulate thelight. For example, a digital micro-mirror device, such as a TexasInstruments Digital Micromirror Device (DMD) may be used to provideangular variation for one or more rows, columns, or pixels such that theoutput location of the light from the film-based lightguide may becontrolled along the length of the coupling lightguide or film-basedlightguide. In this embodiment, the coupling lightguides may extend intoand may define all or a portion of the light emitting area and thefilm-based lightguide may not need a body region or full body region foremitting light and/or mixing light from the coupling lightguides. Otherangular modulation devices may be used to modulate and control the angleof light corresponding to rows, columns, or pixels such as uniaxial orbiaxial scanners (including galvanometric or Microelectromechanicalsystem (MEMS) scanners or spatial light modulators). In anotherembodiment, the function of varying light redirection for each column(or row) may be incorporated into the spatial light modulator, such asfor example by altering the reflecting surface angle in a reflectivespatial light modulator or providing a transmissive light redirectingelement on the surface of a transmissive spatial light modulator. Inanother embodiment, the spatial light modulator modulates the angle ofthe light in a spatial array using amplitude and/or phase diffraction togenerated angular deviation of light in each columns or row. In thisembodiment, the spatial light modulator may be in the form of a digitaldiffractive optical element.

Optical Storage

In one embodiment, an optical storage device comprises the film-basedlightguide, wherein the light output from the light emitting areaprovides illumination to an amplitude or phase spatial light modulator.In this embodiment, the light output from the light emitting area of thelightguide can have one or more selected from the group: constant phasewavefront, uniform phase wavefront, predetermined phase wavefront,random phase wavefront, compensated phase wavefront, or adjustable phasewavefront across the area or spatially varying across the light emittingarea. In one embodiment, the light from the light emitting areailluminates a spatial light modulator (phase or amplitude) and themodulated light profile is imaged or recorded onto an optical storagematerial. For example, in one embodiment, the light from the lightemitting area of the film-based lightguide illuminates a spatial phasemodulating device (such as a reflective LCOS device) and the lightreflecting or transmitting from the spatial phase modulating device isdirected onto a recording medium along with reference light to record aninterference pattern representing the holographic recording of the phasemodulated light profile from the spatial phase modulating device. In oneembodiment, the optical storage device is a holographic data storagedevice.

Optical Metrology Device

In one embodiment, an optical metrology device comprises the film-basedlightguide, wherein the light output from the light emitting areaprovides illumination to an amplitude or phase spatial light modulator.In this embodiment, the light output from the light emitting area of thelightguide can have one or more selected from the group: constant phasewavefront, uniform phase wavefront, predetermined phase wavefront,random phase wavefront, compensated phase wavefront, or adjustable phasewavefront across the area or spatially varying across the light emittingarea. In one embodiment, the light from the light emitting areailluminates a spatial light modulator (phase or amplitude) and themodulated light is directed (imaged, projected, or allowed to convergeor diverge) toward an object and illuminates the object with anamplitude and/or phase pattern or profile of light. In one embodiment,the optical metrology device comprises an imager that receives the lightreflected from the object (or transmitted through the object)illuminated by the pattern of light from the spatial light modulator andthe pattern of light is subsequently changed. By analyzing the change inthe images of the light reflected from the object and captured by theimager, a three-dimensional depth or surface profile can be generatedfor the illuminated area of the object.

Reconfigurable Optical Add-Drop Multiplexer

In one embodiment, an optical add-drop multiplexer or a componentthereof comprises a film-based lightguide and an amplitude or phasespatial light modulator. In one embodiment, the optical add-dropmultiplexer is a wavelength-division multiplexing system formultiplexing and routing different channels of light into or out of afiber such as a single mode optical fiber. In one embodiment, the arrayof coupling lightguide receives light comprising multiple signals anddirects the light through the film to the spatial light modulator andthe spatial light modulator modulates the light to add or remove one ormore signals. In one embodiment, a surface of the film-based lightguidereceives light modulated in phase and/or amplitude and directs the lightto the coupling lightguides that coupling light out through the stackedarray of coupling lightguides at the light output surface formed fromthe ends of the coupling lightguides (analogous to the light inputsurface of the light input coupler where the optical path is in reversein this embodiment).

Multiple Light Emitting Areas or Displays

In one embodiment, the light emitting device includes two or more lightemitting areas or displays defined by regions with one or moreproperties selected from the group: emit different color gamuts; emitlight within different functional areas of the display; emit light withdifferent angular properties; emit light to illuminate a button, key,keyboard area, or other user interface region; have different sizes orshapes; and are positioned on different sides or surfaces of the device.In one embodiment, the light emitting device includes two or more lightemitting regions with different use modes or different illuminationmodes. A different illumination mode can include one or more differentlight output properties selected from the group: different times in the“on” state or “off” state of illumination; different frequencies ofillumination; different durations of illumination; different colors ofillumination; different color gamuts; different angular light outputprofiles; different spatial light output profiles; different spatialluminance uniformity; and different color, luminances or luminousintensity at a specific angle. For example, in one embodiment, the lightemitting device illuminates a main display and a sub-display. The maindisplay and sub-display could be two light emitting areas defined by thesame spatial light modulator or two light emitting areas defined by twoseparate spatial light modulators. In one embodiment, each lightemitting area or display may be illuminated by the same or differentlightguides and/or light sources. For example, in one embodiment, thelight emitting device has a high color gamut lightguide positioned toilluminate the main display of a device with a main display andsub-display from the front in a first mode using light from monochromered, green, and blue LEDs. In this embodiment, the sub-display can beilluminated by a second lightguide that emits only white light to reducethe power required for illuminating the sub-display (which could includeicons or keys, for example) to the same luminance. In anotherembodiment, a first display region includes an array of color filtersand a second display region does not include an array of color filters.For example, in one embodiment, the sub-display may be designed withouta color filter array such that the monochrome sub-display illuminated bya white (or monochrome) light source can operate at a significantlylower power for the same luminance as the main display with colorfilters since light is not absorbed by a color filter array.

In one embodiment, the device includes two or more lightguides spatiallyseparated in the plane of the active area of the light emitting devicesuch that they can be illuminated independently. In this embodiment, forexample, the edges of one or more lightguides opposite the side of thelightguide with the light input coupler may include a light reflectiveor absorptive coating to prevent light from exiting one lightguide andentering into an adjacent lightguide. In one embodiment, the spatiallyseparated lightguides permit the light emitting display device to have asubstantially uniform thickness.

Light Emitting Device Assembly

In one embodiment, the film-based lightguide is adhered to a display,component of a display, or other component of a light emitting deviceusing lamination and/or one or more of the following: addition ofpressure, addition of heat, laminating a coated layer or region,laminating to a relative position maintaining element, and coating anadhesive onto a substrate or component and joining one component toanother.

In one embodiment, the adhesive functions as a cladding between the coreregion of the lightguide and another component, and reduces the flux oflight absorbed by the RPME due to the lightguide contacting the RPME. Inanother embodiment, the pressure sensitive adhesive increases the yieldstrength or impact strength (Izod or Charpy impact strength, forexample) of the film-based lightguide, light emitting device, and/ordisplay. In one embodiment, an adhesive is positioned between thelightguide and a reflective film, surface of the relative positionmaintaining element, or optical component disposed to receive light fromthe light source and direct it into the input surface of the stack ofcoupling lightguides.

Luminance Uniformity of the Backlight, Frontlight, or Light EmittingDevice

In another embodiment, the light source emitting light into an array ofcoupling lightguides includes light sources of two or more differentcolors (such as a red, green, and blue LED) and the spatial colornon-uniformity, Δu′v′, along a line parallel to the array of couplinglightguides or perpendicular to the optical axis of the light travellingwithin the coupling lightguides at the side of the taper closer to thelight source along the length of the coupling lightguides) measured onthe 1976 u′, v′ Uniform Chromaticity Scale as described in VESA FlatPanel Display Measurements Standard version 2.0, Jun. 1, 2001 (Appendix201, page 249) is less than one selected from the group: 0.2, 0.1, 0.05,0.01, and 0.004. In one embodiment, the color difference, Δu′v′, of twolight sources disposed to emit light into the light input surface isgreater than 0.1 and the spatial color non-uniformity, Δu′v′, of thelight from the two light sources in the coupling lightguide beforeentering the taper region is less than 0.1.

The spatial color non-uniformity of the light across a couplinglightguide at a specific location along a coupling lightguide may bemeasured by cutting the coupling lightguide orthogonal to the opticalaxis of the light traveling within the coupling lightguide andpositioning a spectrometer (or input to a spectrometer such as a fiberoptic collector) along the cut edge in a direction oriented along theoptical axis of the light exiting the coupling lightguide.

In one embodiment, a light emitting device includes a light source, alight input coupler, and a film-based lightguide wherein the 9-spotspatial luminance uniformity of the light emitting surface of the lightemitting device measured according to VESA Flat Panel DisplayMeasurements Standard version 2.0, Jun. 1, 2001 is greater than oneselected from the group: 60%, 70%, 80%, 90%, and 95%. In anotherembodiment, a display includes a spatial light modulator and a lightemitting device including a light source, a light input coupler, and afilm-based lightguide wherein the 9-spot spatial luminance uniformity ofthe light reaching the spatial light modulator (measured by disposing awhite reflectance standard surface such as Spectralon by Labsphere Inc.in the location where the spatial light modulator would be located toreceive light from the lightguide and measuring the light reflectingfrom the standard surface in 9-spots according to VESA Flat PanelDisplay Measurements Standard version 2.0, Jun. 1, 2001) is greater thanone selected from the group: 60%, 70%, 80%, 90%, and 95%. In anotherembodiment, a display includes a spatial light modulator and a lightemitting device including a light source, a light input coupler, and afilm-based lightguide wherein the 9-spot spatial luminance uniformity ofthe display measured according to VESA Flat Panel Display MeasurementsStandard version 2.0, Jun. 1, 2001) is greater than one selected fromthe group: 60%, 70%, 80%, 90%, and 95%.

Color Uniformity of the of the Backlight, Frontlight, or Light EmittingDevice

In one embodiment, a light emitting device includes a light source, alight input coupler, and a film-based lightguide wherein the 9-spotsampled spatial color non-uniformity, Δu′v′, of the light emittingsurface of the light emitting device measured on the 1976 u′, v′ UniformChromaticity Scale as described in VESA Flat Panel Display MeasurementsStandard version 2.0, Jun. 1, 2001 (Appendix 201, page 249) is less thanone selected from the group: 0.2, 0.1, 0.05, 0.01, and 0.004 whenmeasured using a spectrometer based spot color meter. In anotherembodiment, a display includes a spatial light modulator and a lightemitting device including a light source, a light input coupler, and afilm-based lightguide wherein the 9-spot sampled spatial colornon-uniformity, Δu′v′, of the of the light reaching the spatial lightmodulator (measured by disposing a white reflectance standard surfacesuch as Spectralon in the location where the spatial light modulatorwould be located to receive light from the lightguide and measuring thecolor of the standard surface on the 1976 u′, v′ Uniform ChromaticityScale as described in VESA Flat Panel Display Measurements Standardversion 2.0, Jun. 1, 2001 (Appendix 201, page 249) is less than oneselected from the group: 0.2, 0.1, 0.05, 0.01, and 0.004 when measuredusing a spectrometer based spot color meter. In another embodiment, adisplay includes a spatial light modulator and a light emitting deviceincluding a light source, a light input coupler, and a film-basedlightguide wherein the 9-spot sampled spatial color non-uniformity,Δu′v′, of the display measured on the 1976 u′, v′ Uniform ChromaticityScale as described in VESA Flat Panel Display Measurements Standardversion 2.0, Jun. 1, 2001 (Appendix 201, page 249) is less than oneselected from the group: 0.2, 0.1, 0.05, 0.01, and 0.004 when measuredusing a spectrometer based spot color meter.

Angular Profile of Light Emitting from the Light Emitting Device

In one embodiment, the light emitting from at least one surface of thelight emitting device has an angular full-width at half-maximumintensity (FWHM) less than one selected from the group: 120 degrees, 100degrees, 80 degrees, 60 degrees, 40 degrees, 20 degrees and 10 degrees.In another embodiment, the light emitting from at least one surface ofthe light emitting device has at least one angular peak of intensitywithin at least one angular range selected from the group: 0-10 degrees,20-30 degrees, 30-40 degrees, 40-50 degrees, 60-70 degrees, 70-80degrees, 80-90 degrees, 40-60 degrees, 30-60 degrees, and 0-80 degreesfrom the normal to the light emitting surface. In another embodiment,the light emitting from at least one surface of the light emittingdevice has two peaks within one or more of the aforementioned angularranges and the light output resembles a “bat-wing” type profile known inthe lighting industry to provide uniform illuminance over apredetermined angular range. In another embodiment, the light emittingdevice emits light from two opposing surfaces within one or more of theaforementioned angular ranges and the light emitting device is oneselected from the group: a backlight illuminating two displays on eitherside of the backlight, a light fixture providing up-lighting anddown-lighting, a frontlight illuminating a display and having lightoutput on the viewing side of the frontlight that has not reflected fromthe modulating components of the reflective spatial light modulator witha peak angle of luminance greater than 40 degrees, 50 degrees, or 60degrees. In another embodiment, the optical axis of the light emittingdevice is within an angular range selected from the group: 0-20, 20-40,40-60, 60-80, 80-100, 100-120, 120-140, 140-160, 160-180, 35-145,45-135, 55-125, 65-115, 75-105, and 85-95 degrees from the normal to alight emitting surface. In a further embodiment, the shape of thelightguide is substantially tubular and the light substantiallypropagates through the tube in a direction parallel to the longer(length) dimension of the tube and the light exits the tube wherein atleast 70% of the light output flux is contained within an angular rangeof 35 degrees to 145 degrees from the light emitting surface. In afurther embodiment, the light emitting device emits light from a firstsurface and a second surface opposite the first surface wherein thelight flux exiting the first and second surfaces, respectively, ischosen from the group: 5-15% and 85-95%, 15-25% and 75-85%, 25-35% and65-75%, 35-45% and 65-75%, 45-55% and 45-55%. In another embodiment, thefirst light emitting surface emits light in a substantially downwarddirection and the second light emitting surface emits lightsubstantially in an upward direction. In another embodiment, the firstlight emitting surface emits light in a substantially upward directionand the second light emitting surface emits light substantially in adownward direction.

Method of Manufacturing Light Input/Output Coupler

In one embodiment, the lightguide and light input or output coupler areformed from a light transmitting film by creating segments of the filmcorresponding to the coupling lightguides and translating and bendingthe segments such that a plurality of segments overlap. In a furtherembodiment, the input surfaces of the coupling lightguides are arrangedto create a collective light input surface by translation of thecoupling lightguides to create at least one bend or fold.

Film Production

In one embodiment, the film or lightguide is one selected from thegroup: extruded film, co-extruded film, cast film, solvent cast film, UVcast film, pressed film, injection molded film, knife coated film, spincoated film, and coated film. In one embodiment, one or two claddinglayers are co-extruded on one or both sides of a lightguide region. Inanother embodiment, tie layers, adhesion promotion layers, materials orsurface modifications are disposed on a surface of or between thecladding layer and the lightguide layer. In one embodiment, the couplinglightguides, or core regions thereof, are continuous with the lightguideregion of the film as formed during the film formation process. Forexample, coupling lightguides formed by slicing regions of a film atspaced intervals can form coupling lightguides that are continuous withthe lightguide region of the film. In another embodiment, a film-basedlightguide with coupling lightguides continuous with the lightguideregion can be formed by injection molding or casting a material in amold including a lightguide region with coupling lightguide regions withseparations between the coupling lightguides. In one embodiment, theregion between the coupling lightguides and lightguide region ishomogeneous and without interfacial transitions such as withoutlimitation, air gaps, minor variations in refractive index,discontinuities in shapes or input-output areas, and minor variations inthe molecular weight or material compositions.

In another embodiment, at least one selected from the group: lightguidelayer, light transmitting film, cladding region, adhesive region,adhesion promotion region, or scratch resistant layer is coated onto oneor more surfaces of the film or lightguide. In another embodiment, thelightguide or cladding region is coated onto, extruded onto or otherwisedisposed onto a carrier film. In one embodiment, the carrier filmpermits at least one selected from the group: easy handling, fewerstatic problems, the ability to use traditional paper or packagingfolding equipment, surface protection (scratches, dust, creases, etc.),assisting in obtaining flat edges of the lightguide during the cuttingoperation, UV absorption, transportation protection, and the use ofwinding and film equipment with a wider range of tension and flatness oralignment adjustments. In one embodiment, the carrier film is removedbefore coating the film, before bending the coupling lightguide, afterfolding the coupling lightguides, before adding light extractionfeatures, after adding light extraction features, before printing, afterprinting, before or after converting processes (further lamination,bonding, die cutting, hole punching, packaging, etc.), just beforeinstallation, after installation (when the carrier film is the outersurface), and during the removal process of the lightguide frominstallation. In one embodiment, one or more additional layers arelaminated in segments or regions to the core region (or layers coupledto the core region) such that there are regions of the film without theone or more additional layers. For example, in one embodiment, anoptical adhesive functioning as a cladding layer is optically coupled toa touchscreen substrate; and an optical adhesive is used to opticallycouple the touchscreen substrate to the light emitting region offilm-based lightguide, thus leaving the coupling lightguides without acladding layer for increased input coupling efficiency.

In another embodiment, the carrier film is slit or removed across aregion of the coupling lightguides. In this embodiment, the couplinglightguides can be bent or folded to a smaller radius of curvature afterthe carrier film is removed from the linear fold region.

Relative Position Maintaining Element

In one embodiment, at least one relative position maintaining elementsubstantially maintains the relative position of the couplinglightguides in the region of the first linear fold region, the secondlinear fold region or both the first and second linear fold regions. Inone embodiment, the relative position maintaining element is disposedadjacent the first linear fold region of the array of couplinglightguides such that the combination of the relative positionmaintaining element with the coupling lightguide provides sufficientstability or rigidity to substantially maintain the relative position ofthe coupling lightguides within the first linear fold region duringtranslational movements of the first linear fold region relative to thesecond linear fold region to create the overlapping collection ofcoupling lightguides and the bends in the coupling lightguides. Therelative position maintaining element may be adhered, clamped, disposedin contact, disposed against a linear fold region or disposed between alinear fold region and a lightguide region. The relative positionmaintaining element may be a polymer or metal component that is adheredor held against the surface of the coupling lightguides, light mixingregion, lightguide region or film at least during one of thetranslational steps. In one embodiment, the relative positionmaintaining element is a polymeric strip with planar or saw-tooth-liketeeth adhered to either side of the film near the first linear foldregion, second linear fold region, or both first and second linear foldregions of the coupling lightguides. By using saw-tooth-like teeth, theteeth can promote or facilitate the bends by providing angled guides. Inanother embodiment, the relative position maintaining element is amechanical device with a first clamp and a second clamp that holds thecoupling lightguides in relative position in a direction parallel to theclamps parallel to the first linear fold region and translates theposition of the clamps relative to each other such that the first linearfold region and the second linear fold region are translated withrespect to each other to create overlapping coupling lightguides andbends in the coupling lightguides. In another embodiment, the relativeposition maintaining element maintains the relative position of thecoupling lightguides in the first linear fold region, second linear foldregion, or both the first and second linear fold regions and provides amechanism to exert force upon the end of the coupling lightguides totranslate them in at least one direction.

In another embodiment, the relative position maintaining elementincludes angular teeth or regions that redistribute the force at thetime of bending at least one coupling lightguide or maintains an evenredistribution of force after at least one coupling lightguide is bentor folded. In another embodiment, the relative position maintainingelement redistributes the force from bending and pulling one or morecoupling lightguides from a corner point to substantially the length ofan angled guide. In another embodiment, the edge of the angled guide isrounded.

In another embodiment, the relative position maintaining elementredistributes the force from bending during the bending operation andprovides the resistance to maintain the force required to maintain a lowprofile (short dimension in the thickness direction) of the couplinglightguides. In one embodiment, the relative position maintainingelement includes a low contact area region, material, or surface reliefregions operating as a low contact area cover, or region wherein one ormore surface relief features are in physical contact with the region ofthe lightguide during the folding operation and/or in use of the lightemitting device. In one embodiment, the low contact area surface relieffeatures on the relative position maintaining element reduce decouplingof light from the coupling lightguides, lightguide, light mixing region,lightguide region, or light emitting region.

In a further embodiment, the relative position maintaining element isalso a thermal transfer element. In one embodiment, the relativeposition maintaining element is an aluminum component with angled guidesor teeth that is thermally coupled to an LED light source.

In another embodiment, a method of manufacturing a lightguide and lightinput coupler including a light transmitting film with a lightguideregion continuously coupled to each coupling lightguide in an array ofcoupling lightguides where the array of coupling lightguides include afirst linear fold region and a second linear fold region substantiallyparallel to the first fold region, includes the steps: (a) forming anarray of coupling lightguides physically coupled to a lightguide regionin a light transmitting film by physically separating at least tworegions of a light transmitting film in a first direction; (b)increasing the distance between the first linear fold region and thesecond linear fold region of the array of coupling lightguides in adirection perpendicular to the light transmitting film surface at thefirst linear fold region; (c) decreasing the distance between the firstlinear fold region and the second linear fold region of the array ofcoupling lightguides in a direction substantially perpendicular to thefirst linear fold region and parallel to the light transmitting filmsurface at the first linear fold region; (d) increasing the distancebetween the first linear fold region and the second linear fold regionof the array of coupling lightguides in a direction substantiallyparallel to the first linear fold region and parallel to the lighttransmitting film surface at the first linear fold region; and (e)decreasing the distance between the first linear fold region and thesecond linear fold region of the array of coupling lightguides in adirection perpendicular to the light transmitting film surface at thefirst linear fold region; such that the coupling lightguides are bent,disposed substantially one above another, and aligned substantiallyparallel to each other.

In another embodiment, the aforementioned method further includes thestep of cutting through the overlapping coupling lightguides to providean array of input edges of the coupling lightguides that end insubstantially one plane orthogonal to the light transmitting filmsurface. The coupling lightguides may be formed by cutting the film inlines to form slits in the film. In another embodiment, theaforementioned method of manufacture further includes forming an arrayof coupling lightguides in a light transmitting film by cuttingsubstantially parallel lines within a light transmitting film. In oneembodiment, the slits are substantially parallel and equally spacedapart. In another embodiment, the slits are not substantially parallelor have non-constant separations.

In another embodiment, the aforementioned method further includes thestep of holding the overlapping array of coupling lightguides in a fixedrelative position by at least one selected from the group: clamping themtogether, restricting movement by disposing walls or a housing aroundone or more surfaces of the overlapping array of coupling lightguides,and adhering them together or to one or more surfaces.

In a further embodiment, the input ends and output ends of the array ofcoupling lightguides are each disposed in physical contact with relativeposition maintaining elements during the aforementioned steps (a), (b),(c) and (d).

In one embodiment, a relative position maintaining element disposedproximal to the first linear fold region of the array of couplinglightguides has an input cross-sectional edge in a plane parallel to thelight transmitting film that is substantially linear and parallel to thefirst linear fold region, and a relative position maintaining elementdisposed proximal to the second linear fold region of the array ofcoupling lightguides at the second linear fold region of the array ofcoupling lightguides has a cross-sectional edge in a plane parallel tothe light transmitting film at the second linear fold regionsubstantially linear and parallel to the linear fold region.

In another embodiment, the cross-sectional edge of the relative positionmaintaining element disposed proximal to the first linear fold region ofthe array of coupling lightguides remains substantially parallel to thecross-sectional edge of the relative position maintaining elementdisposed proximal to the second linear fold region of the array ofcoupling lightguides during steps (a), (b), (c), and (d).

In another embodiment, a method of manufacturing a lightguide and lightinput coupler including a light transmitting film with a lightguideregion optically and physically coupled to each coupling lightguide inan array of coupling lightguides, where a first fold region and a secondfold region are defined in the array of coupling lightguides, includesthe steps: (a) translating the first fold region and the second foldregion away from each other in a direction substantially perpendicularto the film surface at the first fold region such that they move towardeach other in a plane parallel to the film surface at the first foldregion and (b) translating the first fold region and the second foldregion away from each other in a direction parallel to the first foldregion such that the first fold region and second fold region movetoward each other in a direction substantially perpendicular to the filmsurface at the first fold region such that the coupling lightguides arebent and disposed substantially one above another.

Angled Teeth

In a further embodiment, the relative position maintaining elementdisposed proximal to the first linear fold region has a cross-sectionaledge in a plane parallel to the light transmitting film surface disposedproximal to the first linear fold region that includes a substantiallylinear section oriented at an angle greater than 10 degrees to the firstlinear fold region for at least one coupling lightguide. In a furtherembodiment, the relative position maintaining element has saw-tooth-liketeeth oriented substantially at 45 degrees to a linear fold region ofthe coupling lightguides. In one embodiment, the cross-sectional edge ofthe relative position maintaining element forms a guiding edge to guidethe bend of at least one coupling lightguide. In another embodiment, therelative position maintaining element is thicker than the couplinglightguide that is folded around or near the relative positionmaintaining element such that the relative position maintaining element(or a region such as a tooth or angular extended region) does not cut orprovide a narrow region for localized stress that could cut, crack, orinduce stress on the coupling lightguide. In another embodiment, theratio of the relative position maintaining element or the component(such as an angled tooth) thickness to the average thickness of thecoupling lightguide(s) in contact during or after the folding is greaterthan one selected from the group of 1, 1.5, 2, 3, 4, 5, 10, 15, 20, and25. In one embodiment the relative position maintaining element (orcomponent thereof) that is in contact with the coupling lightguide(s)during or after the folding is greater than one selected from the group:0.05, 0.1, 0.2, 0.3, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 millimeter.

In one embodiment, the array of angled teeth in an RPME include firstedges oriented at a first tooth edge angle to the extended direction ofthe teeth (the direction the teeth extend from the spine, perpendicularto the array direction of the array of teeth) and second tooth edgesoriented at a second tooth edge angle to the extended direction of theteeth wherein the first tooth edge angle and second tooth edge angle aregreater than 0 degrees. In one embodiment, a light input couplerincludes an RPME wherein the extended direction of the teeth is parallelto the extended direction of the array of coupling lightguides and thearray direction of the teeth is parallel to the array direction of thearray of coupling lightguides. In one embodiment, the first edge toothangle is between one selected from the group: 40 degrees and 50 degrees;35 degrees and 55 degrees; 30 degrees and 60 degrees; 25 degrees and 65degrees; 20 degrees and 65 degrees; and 15 degrees and 70 degrees. Inanother embodiment, the second edge tooth angle is one selected from thegroup: 0 degrees, greater than 0 degrees, greater than 5 degrees,greater than 10 degrees, greater than 20 degrees, greater than 25degrees, greater than 0 degrees and less than or equal to 5 degrees,greater than 0 degrees and less than or equal to 10 degrees, greaterthan 0 degrees and less than or equal to 15 degrees; greater than 0degrees and less than or equal to 20 degrees, and between 1 and 20degrees.

In one embodiment, a light input coupler includes a folded and stackedarray of a first coupling lightguide and second coupling lightguideextended from a film body, and the first coupling lightguide has asmaller radius of curvature at the first fold than the second couplinglightguide at the second fold. In this embodiment, an RPME includes afirst tooth and second tooth positioned within the fold of the firstcoupling lightguide and second coupling lightguide, respectively, andthe average thickness of the first tooth at the first fold is less thanthe average thickness of the second tooth at the second fold. The tooththickness direction is the direction perpendicular to the planeincluding the direction the teeth extend from the spine and the arraydirection of the array of teeth. In this embodiment, the larger radiusof curvature of the second coupling lightguide permits a thicker secondtooth and a larger contact area for the second coupling lightguide atthe first edge of the second tooth. The larger contact area candistribute the force from tension during or after the folding operationonto a larger area and reduce the likelihood of the coupling lightguidestearing or creasing. In another embodiment, an RPME includes a firsttooth and a second tooth, and the first edge of the first tooth has afirst average thickness less than the average thickness of the firstedge of the second tooth. In this embodiment, the angled edge can bethicker than other regions of the tooth to reduce the weight and/orvolume the RPME.

In one embodiment, the angled teeth of the RPME include two linear edgeswith a curved region with a first radius of curvature between the twolinear edges. In one embodiment, the first radius of curvature isgreater than one selected from the group: 0.1, 0.5, 1, 2, 4, 8, 10, 20,30, 40, 50, 100, 200, and 500 millimeters. In this embodiment, thecurved region is less likely to cut or tear a coupling lightguide duringfolding, application onto the lightguide, or an alignment operation thana sharp intersection of the edges.

In one embodiment, the angled teeth of the RPME are truncated at thebase (the region where the teeth connect to the spine of the RPME). Forexample, in one embodiment, the angled teeth include two linear edgesthat intersect (or include a curved region between them with a radius ofcurvature) and include truncated linear regions on the opposite ends ofthe edges that may be substantially parallel to the extended directionof the array of coupling lightguides.

In one embodiment, one or more of the angled teeth in a RPME aretruncated where the angled teeth join with the spine or between thefirst edge and second edge. In on embodiment, the length of the firstedges of the angled teeth are less than the width of correspondingcoupling lightguides folded around the teeth and the angled teeth aretruncated such that the coupling lightguide has the flexibility toself-align along the first edge in the folding and/or stacking step. Inanother embodiment, the angled teeth are truncated and the ratio of thelength of the first edge to the width of the coupling lightguide foldedaround the edge for one or more teeth and coupling lightguides is oneselected from the group: less than 1, less than 0.9, less than 0.8, lessthan 0.7, less than 0.6, less than 0.5, greater than 1, greater than1.1, greater than 1.2, greater than 1.3, greater than 1.4, greater than1.5, between 0.1 and 2, and greater than 2. In this embodiment, thereduced first edge lengths and/or truncated teeth reduces the likelihoodof non-uniform stress or tension on the coupling lightguides, reducesthe likelihood of creasing or tearing the coupling lightguides,increases the positional tolerance of the coupling lightguide before thefold or after the fold, or increases the folding or rotational toleranceof the coupling lightguides. In another embodiment, the spine of theRPME includes one or more protrusions, guides, or standoffs positionedto contact the lateral edges of a plurality of folded and stackedcoupling lightguides to limit their position in the first extendeddirection. In one embodiment, the protrusions, guides, or standoffs onthe RPME align the lightguides in the extended direction while reducingthe length (and area) of the lateral edges of the coupling lightguide incontact with the spine of the RPME. In one embodiment, the spineincludes one or more protrusions, guides, or standoffs that contact oneor more lateral edges of the stacked array of coupling lightguides in afirst contact percentage of the total area of the lateral edges of theone or more lateral edges of the stacked array of coupling lightguidesin the region from the end of the fold to the light input surface. Inone embodiment, the first contact percentage is selected from the group:less than 100, less than 90, less than 80, less than 70, less than 60,less than 50, less than 40, less than 30, less than 20, less than 10,less than 5, less than 2, and less than 1 percent. In one embodiment,the reduced contact area reduces the light extraction and/or lightabsorption of light reaching the lateral edges from within the couplinglightguides.

Spine of the RPME

In one embodiment, the RPME includes a spine configured to support anarray of alignment guides or angled teeth. In another embodiment, thespine of an RPME connects an array of angled teeth wherein the spinedoes not extend past the angled teeth portion of the RPME. In thisembodiment, when an array of coupling lightguides are folded 90 degreesand stacked, the lateral edges of the stacked coupling lightguides canbe translated from the fold point in a plane parallel to the lightemitting film by a first fold distance such that array of angled teethare coupled together in the upper regions of the spine (the regions onthe fold side of the RPME) without extending past the angled teeth ofthe RPME. In this embodiment, the total volume of the RPME, and thus theinput coupler can be reduced. In one embodiment, the first fold distanceis the translation distance D_(n). In one embodiment, the width of thespine region is less than or equal to the translation distance D_(n). Inanother embodiment, the angled teeth or guides of the RPME arephysically coupled within the volume of the fold region of the array ofcoupling lightguide defined between the overlapping sections of thearray of coupling lightguides. In a further embodiment, the angled teethor guides of the RPME are physically coupled by a spine that does notextend outside the volume defined between the overlapping sections ofthe array of coupling lightguides in the regions of the fold. In anotherembodiment, the angled teeth or guides of the RPME are physicallycoupled by a spine that does not extend past the lateral edges of thefolded and stacked array of coupling lightguides. In a furtherembodiment, the spine extends along one side (such as the fold side inthe direction of the fold from the lightguide region of the film-basedlightguide) such that the angled teeth or guides intersect the spine onthat side. In a further embodiment, the spine does not extend past theangled teeth of the RPME.

Cut-to-Length Relative Position Maintaining Element

In one embodiment, a relative position maintaining element (RPME) isconfigured to be cut-to-size or separated into two or more parts to beused with different configurations of lightguides, coupling lightguides,or light emitting devices. In one embodiment, the relative positionmaintaining element includes one or more selected from the group: areflective surface; alignment guides for an optical element, lightsource, or element housing a light source; guides for stacking thecoupling lightguides; apertures, grooves, or perforations for cuttingthe stacked array of coupling lightguides; and alignment holes disposedproximate a first end of an elongated relative position maintainingelement. In another embodiment the relative position maintaining elementmay be cut-to-size or separated into two or more parts such that theopposite end is not used. In another embodiment, the RPME includes aplurality of angled teeth and alignment ridges, guides, or holes withinor adjacent each angled tooth. In this embodiment, the last tooth(opposite the light input side) may be aligned with a region, such asthe light mixing region near a lateral edge on the opposite side of thefilm-based lightguide. In one embodiment, the RPME includes an array ofalignment guides (such as angled teeth) and one or more registrationpins or guides. In another embodiment, the RPME includes one or moreseparation mechanisms selected from the group: separation guides,separation grooves, separation perforations, separation voids, cuttingguides, and separation edges such that the RPME may be separated (bycutting or breaking, for example) to reduce the length of an RPME. Forexample, in one embodiment the RPME includes one or more arrays ofperforations in the spine region between the angled teeth such that theRPME can be snapped and broken apart along one of the arrays ofperforations. Similarly, in another example, the RPME includes a grooverecessed into the RPME and parallel to the extended direction of theangled teeth in the spine region between the angled teeth such that theRPME can be snapped and broken apart along the groove. In oneembodiment, the RPME is separated into two smaller RPME's that maintainthe relative position of coupling lightguides in two separate lightinput couplers. In one embodiment, the RPME is separated into three ormore sections that may be used in three or more light input couplers. Inone embodiment, the array of coupling lightguides are folded and stackedbefore cutting the RPME. In another embodiment, the array of couplinglightguides are folded and stacked after cutting the RPME. In anotherembodiment, the RPME is cut or separated after the film-based lightguideis laminated to the display. In a further embodiment, the RPME is cut orseparated before the film-based lightguide is laminated to the display.

In one embodiment, the RPME includes alignment guides such as holes,ridges, openings, teeth, protrusions, or connectors, on one, two, three,or four sides of the RPME. For example, in one embodiment, the RPME islonger in a first direction than a second orthogonal direction andincludes one or more alignment holes near the two ends in the longerdirection. In one embodiment, one or more alignment guides is positionedon the side of the RPME opposite the teeth in the second orthogonaldirection.

Perforated Areas

In one embodiment, the light emitting device includes one or morefunctional layers selected from the group: the film-based lightguide;cladding layer of the film based lightguide; touchscreen layer orsubstrate; hardcoating layer or substrate; anti-glare layer orsubstrate; color filter layer or substrate; electro-optic layer orsubstrate; reflective material, film, layer, or substrate; polarizerlayer or substrate; light redirecting layer or substrate; lightextraction feature film, layer or substrate; impact protection layer orsubstrate; internal coating or layer; conformal coating or layer;circuit board or layer; thermally conducting film, layer or substrate;sealant layer or substrate; spacer layer or substrate; electricallyconducting layer (transparent or opaque) or substrate; anode layer orsubstrate; cathode layer or substrate; active matrix layer or substrate;and passive matrix layer or substrate. In one embodiment, at least onefunctional layer is perforated to allow for tearing of the functionallayer or substrate before, during, or after assembly, forming thecoupling lightguides, folding the coupling lightguides, stacking theends of the coupling lightguides, or adhering the lightguide to adisplay. In one embodiment, the substrate or functional layer isperforated in order to maintain tension or to enable holding of afunctional layer for alignment or positioning during an assembly processand removal of the section on one side of the perforation after theprocess. For example, in one embodiment, the film-based lightguideincludes perforated regions that enable the film to be held undertension, or increased tension from one or more sides during assembly andthe film can be torn in the perforated areas after assembly or anassembly step to reduce the final dimensions of the lightguide. In oneembodiment, the perforations are created by stamping, laser cutting,blade cutting, or embossing. In one embodiment, a wrap includes one ormore guide regions with one or more alignment guide holes, andperforations positioned between the one or more alignment guide holesand the region of the wrap physically coupled to a light input coupleror component thereof. In this embodiment, the alignment guide region canbe removed by tearing along the perforation after adhering the wrap tothe lightguide, for example. In another embodiment, a lightguideincludes one or more guide regions with one or more alignment guideholes, and perforations positioned between the one or more alignmentguide holes and the light emitting region. In this embodiment, thealignment guide region can be removed by tearing along the perforationafter lamination of the lightguide to another film or folding andstacking the coupling lightguides, for example.

Folding and Assembly

In one embodiment, the coupling lightguides are heated to soften thelightguides during the folding or bending step. In another embodiment,the coupling lightguides are folded while they are at a temperatureabove one selected from the group: 50 degrees Celsius, 70 degreesCelsius, 100 degrees Celsius, 150 degrees Celsius, 200 degrees Celsius,and 250 degrees Celsius.

Folder

In one embodiment, the coupling lightguides are folded or bent usingopposing folding mechanisms. In another embodiment, grooves, guides,pins, or other counterparts facilitate the bringing together opposingfolding mechanisms such that the folds or bends in the couplinglightguides are correctly folded. In another embodiment, registrationguides, grooves, pins or other counterparts are disposed on the folderto hold in place or guide one or more coupling lightguides or thelightguide during the folding step.

Assembly Order

In one embodiment, the film-based lightguide includes an array ofcoupling lightguides and the array of coupling lightguides are foldedprior to physically or optically coupling the film-based lightguide tothe light emitting device, display or a component thereof. In anotherembodiment, the array of coupling lightguides are folded afterphysically or optically coupling the film-based lightguide to the lightemitting device, display or a component thereof. In another embodiment,the light emitting device or display includes a light input couplerincluding a folded, stacked array of coupling lightguides and the lightinput coupler is assembled before or after the film-based lightguide islaminated to the display. In one embodiment, the display functions as arelative position maintaining element and adhering the film-basedlightguide to the display maintains the relative position of thecoupling lightguides during the subsequent folding operation.

The following are more detailed descriptions of various embodimentsillustrated in the Figures.

FIG. 1 is a top view of one embodiment of a light emitting device 100including a light input coupler 101 disposed on one side of a film-basedlightguide. The light input coupler 101 includes coupling lightguides104 and a light source 102 disposed to direct light into the couplinglightguides 104 through a light input surface 103 including input edgesof the coupling lightguides 104. In one embodiment, each couplinglightguide 104 includes a coupling lightguide terminating at a boundingedge. Each coupling lightguide is folded such that the bounding edges ofthe coupling lightguides are stacked to form the light input surface103. The light emitting device 100 further includes a lightguide region106 defining a light mixing region 105, a lightguide 107, and a lightemitting region 108. Light from the light source 102 exits the lightinput coupler 101 and enters the lightguide region 106 of the film. Thislight spatially mixes with light from different coupling lightguides 104within the light mixing region 105 as the light propagates through thelightguide 107. In one embodiment, light is emitted from the lightguide107 in the light emitting region 108 due to light extraction features(not shown).

FIG. 2 is a perspective view of one embodiment of a light input coupler200 with coupling lightguides 104 folded in the −y direction. Light fromthe light source 102 is directed into the light input surface 103through or along input edges 204 of the coupling lightguides 104. Aportion of the light from the light source 102 propagating within thecoupling lightguides 104 with a directional component in the +ydirection will reflect in the +x and −x directions from the lateraledges 203 of the coupling lightguides 104 and will reflect in the +z and−z directions from the top and bottom surfaces of the couplinglightguides 104. The light propagating within the coupling lightguidesis redirected by the folds 201 in the coupling lightguides 104 towardthe −x direction.

FIG. 3 is a top view of one embodiment of a light emitting device 500with two light input couplers 101 disposed on the same side of thelightguide region 106. In this embodiment, the light sources 102 areoriented substantially with the light directed toward each other in the+y and −y directions.

FIG. 4 is a top view of one embodiment of a light emitting backlight1000 configured to emit red, green, and blue light. The light emittingbacklight 1000 includes a red light input coupler 1001, a green lightinput coupler 1002, and a blue light input coupler 1003 disposed toreceive light from a red light source 1004, a green light source 1005,and a blue light source 1006, respectively. Light from each of the lightinput couplers 1001, 1002, and 1003 is emitted from the light emittingregion 108 due to the light extraction features 1007 which redirect aportion of the light to angles closer to the surface normal within thelightguide region 106 such that the light does not remain within thelightguide 107 and exits the light emitting device 1000 in a lightemitting region 108. The pattern of the light extraction features 1007may vary in one or more of a size, a space, spacing, a pitch, a shape,and a location within the x-y plane or throughout the thickness of thelightguide in the z direction.

FIG. 5 is a cross-sectional side view of one embodiment of a lightemitting device 1100 including the light input coupler 101 and thelightguide 107 with a reflective optical element 1101 disposed adjacentthe cladding region 602 and a light source 1102 with an optical axis inthe +y direction disposed to direct light into the coupling lightguides104. Light from the light source 1102 propagates through the couplinglightguides 104 within the light input coupler 101, through the lightmixing region 105, and through the core layer 601 of the lightguide 107within light emitting region 108 of the lightguide region 106. Referringto FIG. 5, a first portion of light 1104 reaching the light extractionfeatures 1007 is redirected toward the reflecting optical element 1101at an angle less than the critical angle such that the light can escapethe lightguide 107, reflect from the reflective optical element 1101,pass back through the lightguide 107, and exit the lightguide 107through the light emitting surface 1103 of the light emitting region108. A second portion of light 1105 reaching the light extractionfeatures 1007 is redirected toward the light emitting surface 1103 at anangle less than the critical angle, escapes the lightguide 107, andexits the lightguide 107 through the light emitting surface 1103 of thelight emitting region 108.

FIG. 6 is a perspective view of one embodiment of a light emittingdevice 1500 wherein the light mixing region 105 of the lightguide 107wraps around a relative position maintaining element 1501 and a stack ofcoupling lightguides 104 that extend from the lightguide 107 and arestacked in the y direction. The relative position maintaining element1501 substantially maintains the relative position of the couplinglightguides 104 during and/or after folding. The light source 102 isoperatively coupled to the relative position maintaining element 1501and directs light into the light input surfaces 204 of the couplinglightguides 104 such that the light propagates through the couplinglightguides 104, through the light mixing region 105 that is wrappedaround the coupling lightguides 104, and exits the lightguide 107 in thelight emitting region 108. The light source 102 may, for example, beoperatively coupled to the relative position maintaining element 1501 byadhesion, clamping, physical constraint, or another suitable physicalcoupling device or method. Similarly, one or more coupling lightguides104, the lightguide 107, or a region of the lightguide 107 such as thelight mixing region 105 may be adhered or otherwise operatively coupledto the relative position maintaining element 1501. Operatively couplingone or more elements of the light emitting device 1500 can reduce totaldevice volume, decrease the likelihood of contaminants entering intoregions between components, and prevent one or more elements fromunwrapping or unfolding. In one embodiment, the lightguide 107 isadhered to itself in the region of the wrap using an adhesive such as asuitable pressure sensitive adhesive that may be a cladding layer. Inanother embodiment, the light emitting device includes one or moretapered, angled, or non-folding coupling lightguides 104 and the lightsource 102 is positioned between the planes defined by the lateral edges1502 of the lightguide 107 (parallel to the x-y planes in FIG. 6) toreduce the dimension of the device in the z direction.

FIG. 7 is a top view of one embodiment of a coupling lightguide 1610 a,1610 b, and 1610 c in three different positions 1601, 1602, and 1603,respectively. FIG. 7 illustrates the translated distance of the foldedcoupling lightguide 1610 b, 1610 c from the fold line 1609 in theextended direction 1614 when folded beginning at a fold point 1608 at 90degrees for two different radii. In this embodiment, the fold line 1609is the line including the fold points 1608 at which the couplinglightguides (such as 1610 b, 1610 c) begin to fold and, in thisembodiment, is perpendicular to the extended direction 1614 of thecoupling lightguides 1610 b, 1610 c for a 90 degree fold. In thisembodiment, the width of the coupling lightguide 1610 a, 1610 b, 1610 cis shown reduced for illustrative purposes and clarity. The couplinglightguide 1610 a extends from the lightguide 107 in the extendeddirection 1614 (parallel to the −x direction) in an unfolded position1601 (shown in dotted lines). The coupling lightguide 1610 b in thesecond position 1602 is folded to a first radius of curvature in the +zdirection and +y direction to result in a 90 degree fold (the couplinglightguide axis 1612 is 90 degrees from the extended direction 1614). Inthe second position 1602 (shown in dotted lines), the couplinglightguide 1610 b has a first radius of curvature, R1. In the thirdlocation 1603, the coupling lightguide 1610 c has a second radius ofcurvature, R2 larger than first radius of curvature R1. The firsttranslated distance, D1, in the extended direction (in the x-y plane) ofthe midpoint 1606 of the coupling lightguide 1610 b for the secondposition 1602 is: D₁=√{square root over (2)}/2×π×R₁. The secondtranslated distance, D2, in the extended direction (in the x-y plane) ofthe midpoint 1604 of the coupling lightguide 1610 c for the thirdposition 1603 is: D₂=√{square root over (2)}/2×π×R₂. With a largerradius of curvature, R2, the coupling lightguide 1610 c at the thirdlocation 1603 is translated a larger distance (D2>D1) from the fold line1609. An array of coupling lightguides extending in the extendeddirection 1614 and positioned along the fold line 1609 in the +ydirection from the first fold point 1608 is staggered laterally (xdirection) due to variations in radii of curvature.

FIG. 8 is a top view of one embodiment of a light input coupler 1700including a film-based lightguide 107 with staggered couplinglightguides 1701, 1702, 1703, 1704, and 1705. In this embodiment, thecoupling lightguides 1701, 1702, 1703, 1704, and 1705 extend from thelightguide 107 in an extended direction 1614 (parallel to the −xdirection) and are folded in the +z and −y directions around the 45degree angled teeth 1707 of a relative positioning maintaining element3301. The coupling lightguides 1701, 1702, 1703, 1704, and 1705 arefolded along the fold line 1609 and for clarity shown extending past acut line 1706 where the coupling lightguides would normally be cut (orwould be cut initially during fabrication from the film-based lightguide107). In this embodiment, the coupling lightguides 1701, 1702, 1703,1704, and 1705 have staggered light input surfaces 1708 translated inthe extended direction 1614 perpendicular to the fold line 1609. Thefirst coupling lightguide 1701 is translated from the fold line 1609 bya first translated distance D1. The fifth coupling lightguide 1705 istranslated from the fold line 1609 by a fifth translated distance D5.Because the radius of curvature of the fifth coupling lightguide 1705 islarger than the radius of curvature of the first coupling lightguide1701, the fifth translated distance D5 is larger than the firsttranslated distance D1.

FIG. 9 is a top view of one embodiment of a light emitting device 2300including a plurality of coupling lightguides 104 with a plurality offirst reflective surface edges 3908 and a plurality of second reflectivesurface edges 3907 within each coupling lightguide 104. In theembodiment shown in FIG. 9, three light sources 102 are disposed tocouple light into respective light input edges 204 at least partiallydefined by respective first reflective surface edges 3908 and secondreflective surface edges 3907.

FIG. 10 is an enlarged perspective view of the coupling lightguides 104of FIG. 9 with the light input edges 204 disposed between the firstreflective surface edges 3908 and the second reflective surface edges3907. The light sources 102 are omitted in FIG. 10 for clarity.

FIG. 11 is a top view of one embodiment of a film-based lightguide 4900including an array of tapered coupling lightguides 4902 formed bycutting regions in a lightguide 107. The array of tapered couplinglightguides 4902 are formed in a first direction (y direction as shown)with an array dimension length, d1, which is less than a paralleldimension length, d2, of the light emitting region 108 of the lightguide107. A compensation region 4901 is defined within the film-basedlightguide 4900 and does not include tapered coupling lightguides 4902extending therefrom. In this embodiment, the compensation region 4901provides a volume having sufficient length in the y direction to place alight source (not shown) such that the light source does not extend pastthe lower edge 4903 of the lightguide 107. The compensation region 4901of the light emitting region 108 may have a higher density of lightextraction features (not shown) to compensate for the lower input fluxdirectly received from the tapered coupling lightguides 4902 into thelight emitting region 108. In one embodiment, a substantially uniformluminance or light flux output per area in the light emitting region 108is achieved despite the lower level of light flux received by the lightextraction features within the compensation region 4901 of the lightemitting region 108 by, for example, increasing the light extractionefficiency or area ratio of the light extraction features to the areawithout light extraction features within one or more regions of thecompensation region 4901, increasing the width of the light mixingregion 105 between the coupling lightguides 4902 and the light emittingregion 108, decreasing the light extraction efficiency or the averagearea ratio of the light extraction features to the areas without lightextraction features in one or more regions of the light emitting region108 outside the compensation region 4901, or any suitable combinationthereof.

FIG. 12 is a perspective top view of one embodiment of a light emittingdevice 5000 including the film-based lightguide 4900 shown in FIG. 11and a light source 102. In this embodiment, the tapered couplinglightguides 4902 are folded in the −y direction toward the light source102 such that the light input edges 204 of the coupling lightguides 4902are disposed to receive light from the light source 102. Light from thelight source 102 propagating through the tapered coupling lightguides4902 exits the tapered coupling lightguides 4902 and enters into thelight emitting region 108 generally propagating in the +x directionwhile expanding in the +y and −y directions. In this embodiment, thelight source 102 is disposed within the region that did not include atapered coupling lightguide 4902 and the light source 102 does notextend in the y direction past a lower edge 4903 of the light emittingdevice 5000. By not extending past the lower edge 4903, the lightemitting device 5000 has a shorter overall width in the y direction.Furthermore, the light emitting device 5000 can maintain the shorterdimension, d3, in the y direction (shown in FIG. 12) when the taperedcoupling lightguides 4902 and the light source 102 are folded under (−zdirection and then +x direction) the light emitting region 108 along thefold (or bend) line 5001.

FIG. 13 is top view of one embodiment of a film-based lightguide 5800including an array of oriented coupling lightguides 5801 orientedparallel to a first direction 5806 at a coupling lightguide orientationangle 5808 from the second direction 5807 perpendicular to the direction(y-direction) of the array of coupling lightguides 5801 at the lightmixing region 5805. The array of oriented coupling lightguides 5801includes tapered light collimating lateral edges 5803 adjacent the inputsurface 5804 and light turning lateral edges 5802 between the lightinput surface 5804 and the light mixing region 5805 of the film-basedlightguide 107. In this embodiment, light from a light source (notshown) disposed to emit light into the light input surface 5804 when thearray of oriented coupling lightguides 5801 are folded propagates withits optical axis parallel to the first direction 5806 of the array oforiented coupling lightguides 5801 and the optical axis is turned by thelight turning lateral edges 5802 such that the optical axis issubstantially parallel to the second direction 5807 perpendicular to thedirection (y-direction) of the array of oriented coupling lightguides5801 at the light mixing region 5805. In this embodiment, when theoriented coupling lightguides 5801 are folded, the light source can bepositioned between the planes (parallel to the z direction) includingthe lateral edges (5809, 5810) of the lightguide 107 such that a deviceor display including the light emitting device with the film-basedlightguide 5800 does not require a large frame or a border regionextending significantly past the lateral edges (5809, 5810) of thefilm-based lightguide in the y direction (as folded once or when thearray of oriented coupling lightguides 5801 are folded and the lightsource, the array of oriented coupling lightguides 5801, and the lightmixing region 5805 are folded behind the light emitting region 108 ofthe film based lightguide 107). The array of oriented couplinglightguides 5801 permit the light source to be positioned between theplanes including the lateral edges (5809, 5810) of the film-basedlightguide and the light turning lateral edges 5802 redirect the opticalaxis of the light toward the direction 5807 perpendicular to thedirection (y-direction) of the array of oriented coupling lightguides5801 at the light mixing region 5805 such that the optical axis of thelight is oriented substantially parallel to the second direction 5807when the light is extracted by light extraction features (not shown)with light redirecting surface oriented substantially parallel to thearray direction (y direction) of the array of oriented couplinglightguides 5801.

FIG. 14 is a cross-sectional side view of one embodiment of a spatialdisplay 3600 including a frontlight 3603 optically coupled to areflective spatial light modulator 3601. The frontlight 3603 includes afilm-based lightguide 3602 with the light extracting features 1007 thatdirect light to the reflective spatial light modulator 3601 at anglesnear the surface normal of the reflective spatial light modulator 3601.In one embodiment, the reflective spatial light modulator 3601 is anelectrophoretic display, a microelectromechanical system (MEMS)-baseddisplay, or a reflective liquid crystal display. In one embodiment, thelight extraction features 1007 direct one of 50%, 60%, 70%, 80%, and 90%of the light exiting the frontlight 3603 toward the reflective spatiallight modulator 3601 within an angular range of 60 degrees to 120degrees from the light emitting surface of the frontlight 3603.

FIG. 15 is a cross-sectional side view of one embodiment a lightemitting display 1550 with a film-based lightguide 1551 physicallycoupled to a flexible display connector 1556. In this embodiment, thereflective spatial light modulator 1559 includes a bottom substrate 1554and the film-based lightguide 1551 is a top substrate. Light 1552 fromthe light source 102 physically coupled to the flexible displayconnector 1556 is directed into the film-based lightguide 1551 and isredirected by light extraction features 1561 to the active layer 1553where the light 1552 reflects and passes back through the film-basedlightguide 1551, and the upper cladding layer 1557, and exits the lightemitting display 1550.

FIG. 16 is a perspective view of one embodiment of a light emittingdevice 3800 including a film-based lightguide 3802 physically coupled toa flexible connector 1556 for the reflective spatial light modulator1559 with a light source 102 disposed on a circuit board 3805 physicallycoupled to the flexible connector 1556. In this embodiment, thereflective spatial light modulator 1559 includes an active layer 1553positioned between a bottom substrate 1554 and a top substrate 1650. Thetop substrate 1650 of the reflective spatial light modulator 1559 isoptically coupled to the film-based lightguide 3802 using an adhesivecladding layer 3806.

FIG. 17 is a top view of one embodiment of a film-based lightguide 3900including an array of coupling lightguides 3901, 3902, 3903, 3904, 3905extended from a lightguide region 106 of a lightguide 107. The firstcoupling lightguide 3901 has an edge separation distance (Es) from thelateral edge 3906 of the adjacent side of the film-based lightguide3900. In this embodiment, the separation distance of the couplinglightguides (Cs1, Cs2, Cs3, Cs4) along the side of the film-basedlightguide varies. The first coupling lightguide separation distance(Cs1) between the first coupling lightguide 3901 and the second couplinglightguide 3902 is larger than the second separation distance (Cs2)between the second coupling lightguide 3902 and the third couplinglightguide 3903. The third coupling lightguide separation distance (Cs3)between the third coupling lightguide 3903 and the fourth couplinglightguide 3904 is larger than the fourth separation distance (Cs4)between the fourth coupling lightguide 3904 and the fifth couplinglightguide 3905. As shown in FIG. 39, Cs1>Cs2>Cs3>Cs4, however, thevarying spacing does not need to be continuously decreasing along a sideof a film based lightguide 107 and other increasing, decreasing orvariations of separation distances may be used in other embodiments.

FIG. 18 is a perspective view of one embodiment of a light input couplerand lightguide 3300 including a relative position maintaining element3301 disposed proximal to a linear fold region 2902. In this embodiment,the relative position maintaining element 3301 has a cross-sectionaledge 2971 in a plane (x-y plane as shown) parallel to the lighttransmitting film surface 2970 disposed proximal to the linear foldregion 2902 that includes a substantially linear section 3303 orientedat an angle 3302 greater than 10 degrees to the direction 2906 parallelto the linear fold region 2902 for at least one coupling lightguide 104.In one embodiment, a substantially linear section 3303 is disposed at anangle of about 45 degrees to a direction parallel to the linear foldregion 2902.

FIG. 19 is a perspective view of one embodiment of a relative positionmaintaining element (RPME) 9100 including a spine 9101 defined within aspine region 9122 and angled teeth 9107 extending from the spine 9101 inthe teeth extended direction 9109 (parallel to the +x direction)orthogonal to the array direction 9111 (parallel to the y direction) ofthe angled teeth 9107. In this embodiment, the angled teeth 9107 includefirst edges 9108 oriented at a first tooth edge angle 9110 from theteeth extended direction 9109 and second edges 9105 oriented at a secondtooth edge angle 9104 from the teeth extended direction 9109 in the x-yplane. The first edges 9108 and the second edges 9105 have curved edgeprofiles 9102 in the z direction. The curved edge profile 9012 can, forexample, reduce the likelihood of tearing a coupling lightguide (notshown) by eliminating a sharp angle between the edges 9108, 9105 and thetop surfaces 9112 and bottom surfaces 9113 of the RPME 9100. The curvededge profile 9012 permits a greater contact surface area (the curvededge profile 9102) for a coupling lightguide (not shown) folded aroundthe edges such that the force due to tension is spread over a largerarea than a 90 degree flat edges (where the force is typicallyconcentrated along the linear edge interface between the surfaces) andtherefore the coupling lightguide is less likely to tear. Theintersection between the first edges 9108 and the second edges 9105 is acurved intersection 9103 in a cross-sectional plane parallel to the x-yplane. The curved intersection 9103 prevents a sharp intersectionbetween the first edges 9108 and the second edges 9105 that could causea tear in a coupling lightguide during assembly, folding, or stacking.In the embodiment shown in FIG. 19, the angled teeth 9107 have atruncated section 9106 between the spine 9122 and the first edges 9108.The truncated section 9106 of the angled teeth 9107 allows for a higherangular and/or positional tolerance for coupling lightguides (not shown)to position themselves against the first edges 9108 when they are foldedaround the angled teeth 9107. In this embodiment, for example, there isno corner formed from an intersection between the first edges 9108 andthe second edges 9105 and the coupling lightguides could slide along thefirst edge 9108 and past the first edge 9108 (toward the spine 9101)without being stopped by a corner at an intersection between the firstedges 9108 and the second edges 9105 at the spine 9101.

FIG. 20 is a top view of one embodiment of a film-based lightguide 9000including coupling lightguides 9001, 9002, 9003, 9004, 9005, 9006, 9007,and 9008 cut from a lightguide 107 and separated from the light emittingregion 108 by a light mixing region 9010. The light mixing region 9010extends past the light emitting region 108 far lateral edge 9014 in afirst direction 9013 orthogonal to the extended direction 9012 of thecoupling lightguides 9001, 9002, 9003, 9004, 9005, 9006, 9007, and 9008.Light 9015 propagating through the eighth coupling lightguide 9008(shown as light 9015 propagating before the coupling lightguides 9001,9002, 9003, 9004, 9005, 9006, 9007, and 9008 folded in the +z and −ydirection for clarity) reflects from an angled light mixing regionlateral edge 9011 toward the light emitting region 108. The angled lightmixing region lateral edge 9011 is oriented at a first extendedorientation angle 9019 to the extended direction 9012 to direct light9015 from the light mixing region 9010 toward the light emitting region108 of the lightguide 107. In this embodiment, light 9015 totallyinternally reflects from an internal light directing edge 9016 formed bya cut in the lightguide 107, to direct it closer to the far area 9017(the area of the light emitting region 108 further from the light inputsurface (not shown) of the folded and stacked coupling lightguides 9001,9002, 9003, 9004, 9005, 9006, 9007, and 9008 when they are folded in the+z and −y direction) of the light emitting region 108 closer to thelight emitting region far lateral edge 9014. In this embodiment, theeighth coupling lightguide 9008 can direct more light to the far area9017 of the light emitting region 108 to increase the light fluxarriving to the far area to compensate for the reduced light fluxrelative to the near area 9018 of the light emitting region 108 due tomore flux being absorbed in the longer coupling lightguides (the eighthcoupling lightguide 9008 and the seventh coupling lightguide 9007, forexample) than the shorter coupling lightguides (the first couplinglightguide 9001 and the second coupling lightguide 9002, for example).

FIG. 21 is a cross-sectional side view of a portion of one embodiment ofa spatial display 9200 illuminated by a frontlight 9211 including afilm-based lightguide 9210 optically coupled to a reflective spatiallight modulator 3601 using an adhesive 9206 (such as an acrylate-basedpressure sensitive adhesive) in the active area 9208 of the reflectivespatial light modulator 3601. After exiting the light source (not shown)and the folded, stacked coupling lightguides (not shown) light 9212exits the light mixing region 9209 of the film-based lightguide 9210 andreflects from the light extracting features 1007 on the surface of thefilm-based lightguide 9210 toward the reflective spatial light modulator3601 at angles near the surface normal 9202 of the reflective spatiallight modulator 3601. The light 9212 reflects from the reflectivespatial light modulator 3601 and passes back through the film-basedlightguide 9210 and out of the spatial display 9200. A scratch resistanthardcoating 9204 on a hardcoating substrate 9203 protects the outer topsurface 9207 of the spatial display 9200 and is optically coupled to thefilm-based lightguide 9210 using an adhesive 9205 (such as a siliconebased pressure sensitive adhesive). In this embodiment, the adhesivebetween the hardcoating substrate 9205 and the film-based lightguide9210, and the adhesive between the film-based lightguide 9210 and thereflective spatial light modulator 3601 also function as cladding layersfor the film-based lightguide 9210 and are shown partially coated in aregion extended in the active area of the display but not coatedcompletely across the light mixing region 9209 of the film-basedlightguide 9206.

FIG. 22 is a top view of one embodiment of a light emitting device 9250with a first light input coupler 9255 and second light input coupler9256 positioned on opposite sides of the lightguide 107. The first lightinput coupler 9255 includes a first stacked array of couplinglightguides 9261. The first light input coupler 9255 also includes afirst light source 9251 positioned to emit light into a first lightinput surface 9259 of the first stacked array of coupling lightguides9261 and a first photodetector 9252 positioned receive light from thefirst light input surface 9259. The second light input coupler 9256includes a second stacked array of coupling lightguides 9262. The secondlight input coupler 9256 also includes a second light source 9253positioned to emit light into a second light input surface 9260 of thesecond stacked array of coupling lightguides 9262 and a secondphotodetector 9254 positioned receive light from the second light inputsurface 9260. In this embodiment, the second photodetector 9254 candetect light from the first light source 9251 that propagates throughthe first stacked array of coupling lightguides 9261, a first lightmixing region 9257, the light emitting region 108, a second light mixingregion 9258, and the second stacked array of coupling lightguides 9262.Similarly, the first photodetector 9252 can detect light from the secondlight source 9253 that propagates through the second stacked array ofcoupling lightguides 9262, the second light mixing region 9258, thelight emitting region 108, the first light mixing region 9257, and thefirst stacked array of coupling lightguides 9261. For example, in oneembodiment, the first light source 9251 is briefly turned on while thesecond light source 9253 is turned off and the second photodetector 9254measures the intensity of light received after passing through theregions of the lightguide 107. By comparing the relative intensity oflight over time, the electrical power provided to the first light source9251 can be increased to account for light output degradation of thefirst light source 9251 and/or increased light absorption through thefilm-based lightguide 107 (such as from the film yellowing over time) tosubstantially maintain a constant light output from the light emittingarea 108 of the light emitting device 9250 (such as, for example, aconstant luminance of the light emitting region 108 or a constantluminous intensity from the light emitting region 108 at zero degreesfrom the surface normal to the light emitting region 108). Similarly,the relative intensity of the light reaching the first photodetector9252 from the second light source 9253 can be evaluated and theelectrical power provided to the second light source 9253 may beadjusted accordingly to maintain a substantially constant light outputfrom the light emitting area 108 of the light emitting device 9250. Inone embodiment, the first light source 9251 includes a light emittingdiode emitting light in a first wavelength bandwidth; and the secondlight source 9253 includes a light emitting diode emitting light in asecond wavelength bandwidth. In another embodiment, the firstphotodetector 9252 includes a light emitting diode driven in reversemode to detect light intensity within the second wavelength bandwidth;and/or the second photodetector 9254 includes a light emitting diodedriven in reverse mode to detect light intensity within the firstwavelength bandwidth.

FIG. 23 is a top view of one embodiment of a film-based lightguide 9300including an array of coupling lightguides 9301, 9302, 9303, 9304, 9305,9306, and 9307 in an array direction 9313 extended from the lightguide107 in an extended direction 9312 and separated from the light emittingregion 108 by a light mixing region 9310. The film-based lightguide 9300further includes a sacrificial coupling lightguide 9308 including aperforation line 9351 defined by a linear array of perforations 9350 cutfrom the lightguide 107. The perforation line 9351 separates the topcover region 9353 from the side cover region 9352. In this embodiment,the far lateral edge 9354 of the sacrificial coupling lightguide 9308extends past the lateral edge 9356 of the light emitting region 108 andincludes an angled edge 9355. Also, the sacrificial coupling lightguide9308 does not extend past the seventh coupling lightguide 9307 in theextended direction 9312.

FIG. 24 is a perspective view of the film-based lightguide 9300 of FIG.23 wherein the array of coupling lightguides 9301, 9302, 9303, 9304,9305, 9306, and 9307 are folded and stacked in the −y direction and the+z direction to form a light input surface 9382 to receive light from alight source (not shown). The sacrificial coupling lightguide 9308 isalso folded in the −y and +z direction such that the top cover region9353 is positioned above the stack of coupling lightguides 9301, 9302,9303, 9304, 9305, 9306, and 9307. The side cover region 9352 is bentalong the perforation line 9351 in the −z direction such that the sidecover region 9352 is positioned adjacent the lateral edges 9381 of thecoupling lightguides 9301, 9302, 9303, 9304, 9305, 9306, and 9307. Sincethe sacrificial coupling lightguide 9308 does not extend past theseventh coupling lightguide 9307 in the extended direction 9312 beforefolding (as shown in FIG. 23), the sacrificial coupling lightguide 9308does not extend to the light input surface 9382 after folding and doesnot receive a substantial amount of light from the light source (notshown) positioned adjacent the light input surface 9382. Light that isintentionally or unintentionally coupled into the sacrificial couplinglightguide 9308 can be directed into the light emitting region 108 bytotal internal reflection from the angled edge 9355. The angled edge9355 of the sacrificial coupling lightguide 9308 permits the side coverregion 9352 to be folded down (−z direction) without interfering withthe fold region 9383 of the sacrificial coupling lightguide 9308. Inthis embodiment, the sacrificial coupling lightguide 9308 can protectthe top, seventh coupling lightguide 9307 and the lateral edges 9381 ofthe coupling lightguides 9301, 9302, 9303, 9304, 9305, 9306, and 9307.In another embodiment, a wrap (not shown) extends around the top coverregion 9353 and side cover region 9352 of the sacrificial couplinglightguide 9308 such that the wrap does not coupled light out of thetop, seventh coupling lightguide 9307 or the lateral edges 9381 of thecoupling lightguides 9301, 9302, 9303, 9304, 9305, 9306, and 9307.

FIG. 25 is a cross-sectional side view of a portion of one embodiment ofa spatial display 9600 illuminated by a frontlight 9604 including afilm-based lightguide 9610. The film-based lightguide 9610 is opticallycoupled to a color reflective display 9622 including a color filtersubstrate 9606, a color filter layer 9611, and a reflective spatiallight modulator 9621. In this embodiment, the film-based lightguide 9610is adhered and optically coupled to the color reflective display 9622using a light transmitting adhesive 9620 (such as an optically clearpressure sensitive adhesive) to adhere the film-based lightguide 9610 tothe color filter substrate 9606 in the active area 9608 of the colorreflective display 9622. The color filter layer 9611 includes an arrayof first color filters 9601 and second color filters 9602 separated bynon-active areas 9603 (areas without color filters 9601) of the colorfilter layer 9611. Light 9623, after exiting the light source (notshown) and the folded, stack coupling lightguides (not shown),propagating through the frontlight 9604 exits the lightguide 9610 byreflecting from the light extracting features 1007 on the surface of thefilm-based lightguide 9610 toward the color reflective display 9622 atangles near the surface normal 9607 of the color reflective display9622. The light 9623 is directed toward the first color filters 9601 andsecond color filters 9602 due to the physical and optical properties(such as position and facet angle) of the light extraction features1007. In one embodiment, the light 9623 does not pass through thenon-active areas 9603 of the color filter layer 9601. In anotherembodiment, by aligning the light extraction features 1007 with thefirst color filters 9601 and the second color filters 9602 and directingthe light 9623 through the first color filters 9601 and second colorfilters 9602 at an angle near the surface normal 9607 of the colorreflective display 9622, light 9623 is not directed to the inactiveareas 9603 of the color filter layer 9611 where it could be absorbed. Inthe embodiment illustrated in FIG. 25, a scratch resistant hardcoating9204 on a hardcoating substrate 9203 protects the outer top surface 9207of the spatial display 9600 and is optically coupled to the film-basedlightguide 9610 using an adhesive 9205 (such as a silicone basedpressure sensitive adhesive). In one embodiment, the adhesive 9205between the hardcoating substrate 9205 and the film-based lightguide9610, and the adhesive 9620 between the film-based lightguide 9610 andthe color filter substrate 9606 also function as cladding layers for thefilm-based lightguide 9610 in the active area 9608 of the colorreflective display 9622.

FIG. 26 is a top view of one embodiment of a light emitting device 9400including a first light input coupler 9407 coupling light into asub-display light emitting region 9402 of the film-based lightguide 107.The light emitting device 9400 further includes a second light inputcoupler 9408 and third light input coupler 9409 coupling light into amain display light emitting region 9401 of the film-based lightguide107. Internal light directing edges 9410 defined by a cut 9412 in thelightguide 107 are positioned between the sub-display light emittingregion 9402 and the main display light emitting region 9401 to reflect aportion of the light that would otherwise propagate from the sub-displaylight emitting region 9402 to the main display light emitting region9401, or from the main display light emitting region 9401 to thesub-display light emitting region 9402. In another embodiment, a lightabsorbing material is optically coupled to the film-based lightguide 107in the region between the sub-display light emitting region 9402 and themain display light emitting region 9401 to absorb light that wouldcouple between the regions. For example, in one embodiment, a blackplastic strip or reflective aluminum strip is positioned within the cut9412.

FIG. 27 is a top view of one embodiment of a light emitting device 9500including a main display 9501 and a sub-display 9502 illuminated by thelight emitting device 9400 of FIG. 26. In this embodiment, thesub-display 9502 can provide information with a different use-mode orillumination mode. For example, in one embodiment, the sub-display 9502provides icons 9503 and 9504 that may be illuminated for shorter timeperiods than the main display 9501 or can be illuminated by a singlewhite light emitting diode in the first light input coupler 9407 whichis different, for example, from red, green, and blue light emittingdiodes providing illumination with a larger color gamut in the secondlight input coupler 9408 and third light input coupler 9409. In anotherembodiment, a first film-based lightguide and second film basedlightguide (separated in at least their light emitting regions) are usedto illuminate a main display and sub-display, respectively.

FIG. 28 is a perspective view of one embodiment of a wrapped lightguide9900 including a film based lightguide 107 and a light input coupler9901. The light input coupler 9901 includes an array of couplinglightguides 9906 extending from the lightguide 107 that are folded andstacked to define a light input surface 9903. The coupling lightguides9906 are positioned within a cavity 9905 of a light input couplerhousing 9902. A conformal wrap material 9904 is inserted into the cavity9905 that hardens or sets to maintain their relative positions, protect,and provide a low refractive index cladding for the coupling lightguides9906. In on embodiment, the conformal wrap material 9904 is injectedinto the cavity 9905 of the light input coupler housing 9902 after thelight input coupler housing 9902 is positioned around the couplinglightguides 9906. Also, in this embodiment, the light input surface 9903of the coupling lightguides 9906 extends through an opening 9907 in thelight input coupler housing 9902 such that the light input surface 9903can receive light input.

FIG. 29 is a cross-sectional side view of a portion of one embodiment ofa light emitting device 10000 including the light source 102, thelightguide 107, and a light input coupler 10009. The light input coupler10009 includes the array of coupling lightguides 104 extended from thelightguide 107, folded around a RPME 10008, and stacked with thecoupling lightguide 104 ends defining a light input surface 10003positioned to receive light from the light source 102. The couplinglightguides 104 are aligned laterally (x direction) against a spine edge10018 of the RPME 10008. The light emitting device 10000 furtherincludes a flexible wrap 10001 positioned around the folded, stackedarray of coupling lightguides 104. In one embodiment, the flexible wrap10001 can physically protect the coupling lightguides 104 from scratchesor contamination, maintain the relative position of the couplinglightguides 104 (such as to hold them in a compressed stack to occupy asmall volume), intentionally couple out of the lightguide 107 lightpropagating within the cladding of the lightguide 107, or block straylight from exiting the light input coupler 10009. The wrap 10001includes alignment guide holes 10002 in alignment guide regions 10017that can be used to position the wrap 10001 in a folding device (notshown) such that it can be aligned to the lightguide 107, light inputcoupler 10009, or a component of the light input coupler 10009 duringassembly. The wrap 10001 also includes perforations 10016 that can beused to remove the alignment guide regions 10017 of the wrap 10001including the alignment guide holes 10002. For example, in oneembodiment the alignment guide regions 10017 of the wrap 10001 areremoved after adhering the wrap 10001 to the lightguide 107. The lightemitting device 10000 further includes: a first surface 10011 of thelightguide 107 on the opposite side of the lightguide 107 than the stackof coupling lightguides 104; a surface 10012 including the lateral edges10010 of the coupling lightguides 104; a third surface 10013 includingthe outer surface of the coupling lightguide 104 in the stack ofcoupling lightguides 104 furthest from the lightguide 107; and a fourthsurface 10014 of the lightguide 107 on the same side of the lightguide107 as the stack of coupling lightguides 104. In one embodiment, theflexible wrap 10001 includes a tape with an adhesive on the innersurface 10015 that adheres to one or more surfaces selected from thegroup: the first surface 10011, the second surface 10012, the thirdsurface 10013, and the fourth surface 10014. In one embodiment, the wrap10001 adheres to the first surface 10011 and the fourth surface 10014and holds the coupling lightguides 104 together and toward thelightguide 107 in the z direction. In one embodiment, the wrap 10001does not contact the second surface 10012 and there is an air gapbetween the lateral edges 10010 of the coupling lightguides 104 suchthat the wrap 10001 does not couple light out of the lateral edges 10010of the coupling lightguides 104.

FIG. 30 is a perspective view of one embodiment of a relative positionmaintaining element (RPME) 9800 including a spine 9801 defined within aspine region 9822 and angled teeth 9807 extending from the spine 9801 inthe teeth extended direction 9809 (parallel to the +x direction)orthogonal to the array direction 9811 (parallel to the y direction) ofthe angled teeth 9807. The RPME 9800 includes grooves 9823 parallel tothe teeth extended direction 9809 in the spine region 9822 between theangled teeth 9807 such that the RPME 9800 can be snapped and brokenapart along the grooves 9823. In another embodiment, the RPME 9800includes one or more separation mechanisms defined by perforations (notshown) in the spine region 9822 of the RPME 9800 such that the RPME 9800can be snapped and broken apart along the one or more perforations.

FIGS. 31, 32, and 33 are perspective views of one embodiment of arelative position maintaining element (RPME) 10100 including a spine10106 and angled teeth 10101 extending in the teeth extended direction10109 (parallel to the +y direction) orthogonal to the array direction10110 (parallel to the x direction) of the angled teeth 10101. Theangled teeth 10101 include first edges 10104 and second edges 10105. Thefirst edges 10104 have curved edge profiles in the z direction. In thisembodiment, the angled teeth 10101 extend from the spine 10106 thatconnects them together and are positioned beneath the spine 10106 (shownmost clearly in FIG. 33 where one can see the angled teeth 10101extending past the spine in the x-y plane). By starting the angled teeth10101 from beneath the spine 10106, the volume of the RPME 10100 isreduced because the length of the RPME 10100 in the y direction isreduced relative to extending the angled teeth 10101 from the lateraledge 10108 of the spine 10106. In a this embodiment, the angled teeth10101 of the RPME 10100 are physically coupled by a spine 10106 thatdoes not extend past the angled teeth 10101 in the x-y plane. The RPME10100 further includes a platform region 10102 whereupon one or moreelements of a light emitting device (such as for example, couplinglightguides, light sources, collimating optics, and reflective films)could be adhered to the RPME 10100.

FIG. 34 is a cross-sectional side view of one embodiment of a lightemitting device 3400 comprising the light input coupler 101, afilm-based lightguide 107 comprising a core layer 601 of a core materialwith a core refractive index nm optically coupled to a reflectivespatial light modulator 3408 using a first pressure sensitive adhesivelayer 3407 comprising a first material with a first refractive indexn_(D1). A light source 1102 with an optical axis parallel to the +ydirection (into the page) is positioned to emit light into the foldedstack of coupling lightguides 104. The film-based lightguide 107comprises a plurality of low angle directing features 3503 on the lowersurface 3413 of the core layer 601 of the film-based lightguide 107 andis optically coupled to a light turning film 3403 on the upper surface3414 of the core layer 601 using a second pressure sensitive adhesivelayer 3412 comprising a second material with a second refractive indexnm. The light turning film 3403 comprises a plurality of reflectivelight turning features 3401 on the top surface 3415 of the light turningfilm 3403 opposite the second pressure sensitive adhesive layer 3412. Athird pressure sensitive adhesive layer 3405 optically couples a coverlayer 3406 (such as a protective PET film or touchscreen film, forexample) to the light turning film 3403 over a portion of the topsurface 3415 such that air gaps 3416 are formed at the reflective lightturning features 3401. A light mixing region 105 is positioned betweenthe light input coupler 101 and the light emitting region 108 of thelight emitting device 3400. An opaque layer 3411 is optically coupled tothe film-based lightguide 107 in the light mixing region 105 using thesecond pressure sensitive adhesive layer 3412. In this embodiment, theopaque layer 3411 is a light absorbing layer that absorbs at least 70%of the light within a wavelength range between 400 nanometers and 700nanometers that reaches the opaque layer 3411 through the secondpressure sensitive adhesive layer 3412. In this embodiment, first light3409 and second light 3410 from the light source 1102 propagate throughthe coupling lightguides 104 within the light input coupler 101, totallyinternally reflect within the core layer 601 of the film-basedlightguide 107 and propagate through the light mixing region 105 andinto the light emitting region 108 of the film-based lightguide 107.First light 3409 reflects from a low angle directing feature 3503 to asecond angle in the core layer 601 of the lightguide smaller than theincident angle by an average total angle of deviation of less than 20degrees. In this embodiment, the second angle is less than the criticalangle for the interface between the core layer 601 and second pressuresensitive adhesive layer 3412. In this embodiment, n_(DL)>n_(D2)>n_(D1)such that the first light 3409 and the second light 3410 preferentiallyescape a total internal reflection condition within the core layer 601of the film-based lightguide 107 on the upper surface 3414 of the corelayer 601 since the refractive index, n_(D2), of the second pressuresensitive adhesive layer 3412 is greater than the refractive index,n_(D1), of the first pressure sensitive adhesive layer 3407. Aftertransmitting from the core layer 601 into the second pressure sensitiveadhesive layer 3412, the first light 3409 propagates into the lightturning film 3403 and totally internally reflects from a light turningfeature 3401 in the light turning film 3403 to an angle within 30degrees from the thickness direction (parallel to the z direction inthis embodiment) of the film-based lightguide 107. The first light 3409then propagates back through the light turning film 3403, the secondpressure sensitive adhesive layer 3412, the core layer 601, and thefirst pressure sensitive adhesive layer 3407, reflects from thereflective spatial light modulator 3408, passes back through theaforementioned layers in the reverse order, does not interact a secondtime with a light turning feature 3401, and is emitted from the lightemitting device 3400 in the light emitting region 108.

After being redirected by the low angle light directing feature 3503,the second light 3410 propagates from the core layer 601 into the secondpressure sensitive adhesive layer 3412 and into the light turning film3403. The second light 3410 does not intersect a light turning feature3401 on the first pass and totally internally reflects from the topsurface 3415 of the light turning film 3403 between the light turningfeatures 3401 and propagates back through the light turning film 3403,through the second pressure sensitive adhesive layer 3412, through thecore layer 601 and totally internally reflects at the interface betweenthe core layer 601 and the first pressure sensitive adhesive layer 3407,passes back through the aforementioned layers in reverse order andtotally internally reflects from a light turning feature 3401 in thelight turning film 3403 to an angle within 30 degrees from the thicknessdirection (parallel to the z direction in this embodiment) of thefilm-based lightguide 107. The second light 3410 then propagates backthrough the light turning film 3403, the second pressure sensitiveadhesive layer 3412, the core layer 601, and the first pressuresensitive adhesive layer 3407, reflects from the reflective spatiallight modulator 3408, passes back through the aforementioned layers inthe reverse order, and is emitted from the light emitting device 3400 inthe light emitting region 108.

FIG. 35 is a cross-sectional side view of one embodiment of a lightemitting device 3500 comprising the light input coupler 101, afilm-based lightguide 107 comprising a core layer 601 of a core materialwith a core refractive index n_(DL) optically coupled to a reflectivespatial light modulator 3408 using a first pressure sensitive adhesivelayer 3407 comprising a first material with a first refractive indexn_(D1). A light source 1102 with an optical axis parallel to the +ydirection (into the page) is positioned to emit light into the foldedstack of coupling lightguides 104. The film-based lightguide 107comprises a plurality of refractive low angle directing features 3503 onthe upper surface 3414 of the core layer 601 of the film-basedlightguide 107 and is optically coupled to a light turning film 3403 onthe upper surface 3414 of the core layer 601 using a second pressuresensitive adhesive layer 3412 comprising a second material with a secondrefractive index n_(D2). The light turning film 3403 comprises aplurality of reflective light turning features 3401 on the top surface3415 of the light turning film 3403 opposite the second pressuresensitive adhesive layer 3412. A third pressure sensitive adhesive layer3405 optically couples a cover layer 3406 (such as a protective PET filmor touchscreen film, for example) to the light turning film 3403 over aportion of the top surface 3415 such that air gaps 3416 are formed atthe reflective light turning features 3401. A light mixing region 105 ispositioned between the light input coupler 101 and the light emittingregion 108 of the light emitting device 3400. An opaque layer 3411 isoptically coupled to the film-based lightguide 107 in the light mixingregion 105 using the second pressure sensitive adhesive layer 3412. Inthis embodiment, the opaque layer 3411 is a light absorbing layer thatabsorbs at least 70% of the light within a wavelength range between 400nanometers and 700 nanometers that reaches the opaque layer 3411 throughthe second pressure sensitive adhesive layer 3412. In this embodiment,first light 3501 and second light 3502 from the light source 1102propagate through the coupling lightguides 104 within the light inputcoupler 101, totally internally reflect within the core layer 601 of thefilm-based lightguide 107 and propagate through the light mixing region105 and into the light emitting region 108 of the film-based lightguide107. First light 3501 refracts to a new angle smaller than the incidentangle by an average total angle of deviation of less than 20 degrees ata refractive low angle directing feature 3503 such that it propagatesout of the core layer 601 of the lightguide. In this embodiment, aportion of the light from within the core layer 601 that intersects arefractive low angle directing feature 3503 may transmit through therefractive low angle directing feature 3503 and a portion may reflectfrom the low angle directing feature 3503. In this embodiment,n_(DL)>n_(D2)>n_(D1) such that a portion of the light that reflects fromthe low angle directing feature 3503 may reflect at a total angle ofdeviation of less than 20 degrees such that it reflects from theboundary between the core layer 601 and the first pressure sensitiveadhesive layer 3407 and exits the core layer 601 at the upper surface3414 of the core layer 601. After crossing the interface between thecore layer 601 and the second pressure sensitive adhesive, the firstlight 3501 then propagates through the second pressure sensitiveadhesive layer 3412 into the light turning film 3403 and totallyinternally reflects from a light turning feature 3401 in the lightturning film 3403 to an angle within 30 degrees from the thicknessdirection (parallel to the z direction in this embodiment) of thefilm-based lightguide 107. The first light 3501 then propagates backthrough the light turning film 3403, the second pressure sensitiveadhesive layer 3412, the core layer 601, and the first pressuresensitive adhesive layer 3407, reflects from the reflective spatiallight modulator 3408, passes back through the aforementioned layers inthe reverse order, does not interact a second time with a light turningfeature 3401, and is emitted from the light emitting device 3500 in thelight emitting region 108.

After being redirected by the low angle light directing feature 3503,the second light 3502 propagates through the second pressure sensitiveadhesive layer 3412 and into the light turning film 3403. The secondlight 3502 does not intersect a light turning feature 3401 on the firstpass and totally internally reflects from the top surface 3415 of thelight turning film 3403 between the light turning features 3401 andpropagates back through the light turning film 3403, through the secondpressure sensitive adhesive layer 3412, through the core layer 601 andtotally internally reflects at the interface between the core layer 601and the first pressure sensitive adhesive layer 3407, passes backthrough the aforementioned layers in reverse order and totallyinternally reflects from a light turning feature 3401 in the lightturning film 3403 to an angle within 30 degrees from the thicknessdirection (parallel to the z direction in this embodiment) of thefilm-based lightguide 107. The second light 3502 then propagates backthrough the light turning film 3403, the second pressure sensitiveadhesive layer 3412, the core layer 601, and the first pressuresensitive adhesive layer 3407, reflects from the reflective spatiallight modulator 3408, passes back through the aforementioned layers inthe reverse order, and is emitted from the light emitting device 3400 inthe light emitting region 108.

FIG. 36 is a perspective view of one embodiment of a light emittingdevice 3691 comprising a light input coupler 200 with couplinglightguides 104 folded in the −y direction. Light 3692 from the lightsource 102 is directed through a phase compensation optical element 3690into the light input surface 103 through or along input edges 204 of thecoupling lightguides 104. A portion of the light from the light source102 propagating within the coupling lightguides 104 with a directionalcomponent in the +y direction will reflect in the +x and −x directionsfrom the lateral edges 203 of the coupling lightguides 104 and willreflect in the +z and −z directions from the top and bottom surfaces ofthe coupling lightguides 104. The light propagating within the couplinglightguides is redirected by the folds 201 in the coupling lightguides104 toward the −x direction and the light emitting region 108 of thelightguide 107. In this embodiment, the phase compensation element 3690pre-compensates for the phase deviation of the light propagating throughthe coupling lightguides 104 and the lightguide 107 such that a uniformor pre-determined spatial phase output profile of light emitting fromthe light emitting region 108 of the light emitting device 3691 isachieved.

FIG. 37 is a cross-sectional side view of one embodiment of a lightemitting device 3700 comprising the light input coupler 101, afilm-based lightguide 107 comprising a core layer 601 of a core materialwith a core refractive index n_(DL) optically coupled to a light turningfilm 3403 over a portion of the top surface 3704 of the light turningfilm 3403 (such that air gaps 3416 are formed at the reflective lightturning features 3401) using a second pressure sensitive adhesive layer3412 comprising a second material with a second refractive index n_(D2).The reflective spatial light modulator 3408 is optically coupled to thelight turning film 3403 using a third pressure sensitive adhesive layer3405. The light turning film 3403 comprises a plurality of reflectivelight turning features 3401 on the top surface 3705 of the light turningfilm 3403 opposite the third pressure sensitive adhesive layer 3405. Alight source 1102 with an optical axis parallel to the +y direction(into the page) is positioned to emit light into the folded stack ofcoupling lightguides 104. The film-based lightguide 107 comprises aplurality of low angle directing features 3503 on the top surface 3705of the core layer 601 of the film-based lightguide 107 and is opticallycoupled to a cover layer 3406 (such as a protective PET film ortouchscreen film, for example) using a first pressure sensitive adhesivelayer 3407 comprising a first material with a first refractive indexn_(D1).

A light mixing region 105 is positioned between the light input coupler101 and the light emitting region 108 of the light emitting device 3700.An opaque layer 3411 is optically coupled to the film-based lightguide107 in the light mixing region 105 using the first pressure sensitiveadhesive layer 3407. In this embodiment, the opaque layer 3411 is alight absorbing layer that absorbs at least 70% of the light within awavelength range between 400 nanometers and 700 nanometers that reachesthe opaque layer 3411 through the first pressure sensitive adhesivelayer 3407. In this embodiment, first light 3701 from the light source1102 propagates through the coupling lightguides 104 within the lightinput coupler 101, totally internally reflect within the core layer 601of the film-based lightguide 107 and propagates through the light mixingregion 105 and into the light emitting region 108 of the film-basedlightguide 107. First light 3701 reflects from a low angle directingfeature 3503 to a second angle in the core layer 601 of the lightguidesmaller than the incident angle by an average total angle of deviationof less than 20 degrees. In this embodiment, the second angle is lessthan the critical angle for the interface between the core layer 601 andsecond pressure sensitive adhesive layer 3412. In this embodiment,n_(DL)>n_(D2)>n_(D1) such that the first light 3701 preferentiallyescapes a total internal reflection condition within the core layer 601of the film-based lightguide 107 on the lower surface 3706 of the corelayer 601 since the refractive index, n_(D2), of the second pressuresensitive adhesive layer 3412 is greater than the refractive index,n_(D1), of the first pressure sensitive adhesive layer 3407. Aftertransmitting from the core layer 601 into the second pressure sensitiveadhesive layer 3412, the first light 3409 propagates into the lightturning film 3403 and totally internally reflects from a light turningfeature 3401 in the light turning film 3403 to an angle within 30degrees from the thickness direction (parallel to the z direction inthis embodiment) of the film-based lightguide 107. The first light 3409then propagates through the third pressure sensitive adhesive layer 3405and reflects from the reflective spatial light modulator 3408, passesback through the aforementioned layers in the reverse order, does notinteract a second time with a light turning feature 3401, and is emittedfrom the light emitting device 3400 in the light emitting region 108.

In one embodiment, a light emitting device (such as a frontlight for areflective display, for example) comprises a film-based lightguide withthe surfaces of the film defining a first lightguide, the firstlightguide is optically coupled to a light redirecting optical elementor other film and one or more surfaces of the light redirecting opticalelement or other film in combination with a surface of the firstlightguide define a second lightguide, wherein the second lightguide maycomprise the first lightguide. In one embodiment, a reflective displaycomprises a lightguide wherein an effective thickness of the lightguidebounded by total internal reflection interfaces is increased for totallyinternally reflected light within the core layer that is frustrated bythe plurality of light extraction features such that it passes throughthe first cladding layer and totally internally reflects at one of thetotal internal reflection interfaces of a light redirecting opticalelement. In a further embodiment, a first lightguide and a secondlightguide comprise the core layer, the second lightguide defined by aportion of the frustrated totally internally reflected light from thefirst lightguide propagating by total internal reflection between asurface of the first lightguide and an area of a surface of the lightredirecting optical element, wherein the light redirecting features of alight redirecting optical element occupy less than 50% of the surface ofthe light redirecting optical element, the area of the surface of thelight redirecting element is defined between the light redirectingfeatures and reflects by total internal reflection a second portion ofthe frustrated totally internally reflected light from the lightextraction features back through a first cladding layer and into a corelayer of the first lightguide where it totally internally reflects fromthe surface of the first lightguide and is subsequently reflected by alight redirecting feature toward a reflective spatial light modulator.

In one embodiment, a light emitting device comprises: a film lightguideof a lightguide material with a refractive index n_(DL), including abody having a first surface and an opposing second surface; a pluralityof coupling lightguides extending from the body, each couplinglightguide of the plurality of coupling lightguides having an end, theplurality of coupling lightguides folded and stacked such that the endsof the plurality of coupling lightguides define a light input surface;the body of the film comprising a first core layer comprising a firstmaterial with a first refractive index, n_(D1), a second layercomprising a second material with a second refractive index n_(D2) wheren_(DL)>n_(D2)>n_(D1); a plurality of low angle directing featuresoptically coupled to the body of the lightguide; a plurality of lightturning features optically coupled to the lightguide; wherein lightpropagating under total internal reflection at a first angle within thelightguide is redirected by the low angle directing features to a secondangle less than the critical angle of an interface between the corelightguide layer and the second layer, a portion of the redirected lightpropagating through the interface and redirected by the light turningfeatures to an angle within 30 degrees of the thickness direction of thefilm.

In one aspect, a light emitting device including a film with couplinglightguides extending therefrom includes a coupling lightguide RelativePosition Maintaining Element (RPME) including a spine region connectingan array of angled teeth or guides. In another aspect, the angled teethor guides of the RPME are physically coupled by a spine that does notextend outside the volume defined between the overlapping sections ofthe array of coupling lightguides in the regions of the fold. In anotheraspect, the array of angled teeth in an RPME include first edgesoriented at a first tooth edge angle to the extended direction of theteeth (the direction the teeth extend from the spine, perpendicular tothe array direction of the array of teeth) and second edges oriented ata second tooth edge angle to the extended direction of the teeth whereinthe first tooth edge angle and second tooth edge angle are greater than0 degrees.

In another aspect, a lightguide, cladding, or adhesive optically coupledto the lightguide includes a pliable or impact absorbing material. Inanother aspect, the ASTM D2240 Shore A hardness of the lighttransmitting lightguide, adhesive, or component physically and/oroptically coupled to the lightguide is greater than one selected fromthe group: 5, 10, 20, 30, 40, 50, 60, 70, and 80.

In one aspect, a light input coupler for a light emitting deviceincludes a wrap around a stack of coupling lightguides wherein the wrapincludes a film with a Young's modulus less than one selected from thegroup: 10, 8, 6, 4, 2, 1, 0.5, and 0.1 gigapascals. In another aspect,the wrap includes perforations or alignment holes. In another aspect,the wrap material is a conformal material coated or injected into acavity or region including the coupling lightguides.

Exemplary embodiments of light emitting devices and methods for makingor producing the same are described above in detail. The devices,components, and methods are not limited to the specific embodimentsdescribed herein, but rather, the devices, components of the devicesand/or steps of the methods may be utilized independently and separatelyfrom other devices, components and/or steps described herein. Further,the described devices, components and/or the described methods steps canalso be defined in, or used in combination with, other devices and/ormethods, and are not limited to practice with only the devices andmethods as described herein.

While the disclosure includes various specific embodiments, thoseskilled in the art will recognize that the embodiments can be practicedwith modification within the spirit and scope of the disclosure and theclaims.

It is to be understood that the phraseology and terminology used hereinis for the purpose of description and should not be regarded aslimiting. The use of “including,” “comprising,” or “having” andvariations thereof herein is meant to encompass the items listedthereafter and equivalents thereof as well as additional items. Unlessspecified or limited otherwise, the terms “mounted,” “connected,”“supported,” and “coupled” and variations thereof are used broadly andencompass both direct and indirect mountings, connections, supports, andcouplings. Further, “connected” and “coupled” are not restricted tophysical or mechanical connections or couplings.

Reference throughout this specification to “one embodiment” or “anembodiment” may mean that a particular feature, structure, orcharacteristic described in connection with a particular embodiment maybe included in at least one embodiment of claimed subject matter. Thus,appearances of the phrase “in one embodiment” or “an embodiment” invarious places throughout this specification is not necessarily intendedto refer to the same embodiment or to any one particular embodimentdescribed. Furthermore, it is to be understood that particular features,structures, or characteristics described may be combined in various waysin one or more embodiments. In general, of course, these and otherissues may vary with the particular context of usage. Therefore, theparticular context of the description or the usage of these terms mayprovide helpful guidance regarding inferences to be drawn for thatcontext.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, numerous equivalents to thespecific procedures described herein. Such equivalents are considered tobe within the scope of the disclosure. Various substitutions,alterations, and modifications may be made to the embodiments withoutdeparting from the spirit and scope of the disclosure. Other aspects,advantages, and modifications are within the scope of the disclosure.This disclosure is intended to cover any adaptations or variations ofthe specific embodiments discussed herein. Therefore, it is intendedthat this disclosure be limited only by the claims and the equivalentsthereof.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified by the term “about”. Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe foregoing specification and attached claims are approximations thatcan vary depending upon the desired properties sought to be obtained bythose skilled in the art utilizing the teachings disclosed herein.Unless indicated to the contrary, all tests and properties are measuredat an ambient temperature of 25 degrees Celsius or the environmentaltemperature within or near the device when powered on (when indicated)under constant ambient room temperature of 25 degrees Celsius. Unlessotherwise stated, refractive indexes referenced herein are measured atthe yellow doublet sodium D-line, with a wavelength of 589 nanometers.Elements in the figures are not drawn to scale.

What is claimed is:
 1. A display comprising: a. a reflective spatiallight modulator having a reflective surface; b. a lightguide comprising:i). a core layer having opposing surfaces with a thickness not greaterthan 0.5 millimeters therebetween wherein light propagates by totalinternal reflection between the opposing surfaces; ii). a first claddinglayer having a first side optically coupled to the core layer and anopposing second side; iii). a lightguide region; iv). an array ofcoupling lightguides continuous with the lightguide region, eachcoupling lightguide of the array of coupling lightguides terminating ina bounding edge, and each coupling lightguide folded in a fold regionsuch that the bounding edges of the array of coupling lightguides arestacked; and v). a light emitting region comprising a plurality of lightextraction features arranged in a pattern that varies spatially in thelight emitting region, the plurality of light extraction featuresfrustrating totally internally reflected light propagating within thecore layer such that light exits the core layer in the light emittingregion into the first cladding layer; c. a light source positioned toemit light into the stacked bounding edges, the light propagating withinthe array of coupling lightguides to the lightguide region, with lightfrom each coupling lightguide combining and totally internallyreflecting within the lightguide region; and d. a light redirectingoptical element optically coupled to the second side of the firstcladding layer, the light redirecting optical element comprising aplurality of light redirecting features directing frustrated totallyinternally reflected light from the plurality of light extractionfeatures toward the reflective spatial light modulator, the plurality oflight redirecting features occupying less than 50% of a surface of thelight redirecting optical element in the light emitting region, whereinthe core layer has an average thickness in the light emitting region,the light emitting region has a largest dimension in a plane of thelight emitting region orthogonal to a thickness direction of the corelayer, and the largest dimension of the light emitting region divided bythe average thickness of the core layer in the light emitting region isgreater than
 100. 2. The display of claim 1 wherein the core layer ofthe lightguide further comprises a light mixing region positioned toreceive light from each coupling lightguide prior to the light enteringthe light emitting region and a ratio of an average thickness of aregion defined by a plurality of interfaces defining the total internalreflection of light propagating from a first end to an opposite secondend of the light emitting region to an average thickness of the lightmixing region is greater than
 1. 3. The display of claim 1 wherein thelightguide further comprises a second cladding layer having a firstsurface optically coupled to the core layer on a side of the core layeropposite the first cladding layer and at least one of the first claddingand the second cladding comprises an adhesive.
 4. The display of claim 1wherein an effective thickness of the lightguide bounded by a pluralityof total internal reflection interfaces is increased for totallyinternally reflected light within the core layer that is frustrated bythe plurality of light extraction features such that the frustratedlight passes through the first cladding layer and totally internallyreflects at a first total internal reflection interface of the pluralityof total internal reflection interfaces.
 5. The display of claim 4wherein the first total internal reflection interface includes thesurface of the light redirecting optical element.
 6. The display ofclaim 5 wherein the frustrated light totally internally reflected at thesurface of the light redirecting optical element totally internallyreflects at a second total internal reflection interface between thecore layer and a second cladding layer of the lightguide.
 7. The displayof claim 6 wherein a portion of the frustrated light that reflects atthe second total internal reflection interface between the core layerand the second cladding layer is subsequently redirected by a firstlight redirecting feature of the plurality of light redirecting featurestoward the reflective spatial light modulator.
 8. The display of claim 6wherein the first cladding layer has a first refractive index, thesecond cladding layer has a second refractive index less than the firstrefractive index, and the core layer has a core refractive index greaterthan the first refractive index and the second refractive index.
 9. Thedisplay of claim 5 wherein an area of the surface of the lightredirecting optical element between the plurality of light redirectingfeatures is substantially planar.
 10. The display of claim 9 whereineach of the plurality of light extraction features is a low angledirecting feature that redirects light at a first angle of incidence toa second angle with an average total deviation less than 6 degrees. 11.The display of claim 9 wherein each of the plurality of light extractionfeatures is a low angle directing feature that redirects light at afirst angle of incidence to a second angle with an average totaldeviation less than 3 degrees.
 12. The display of claim 9 wherein eachof the plurality of light extraction features is a low angle directingfeature that redirects light at a first angle of incidence to a secondangle with an average total deviation less than an angular differencebetween a first critical angle and a second critical angle, the firstcritical angle defined by the first refractive index and the corerefractive index and the second critical angle defined by the secondrefractive index and the core refractive index.
 13. The display of claim9 wherein each of the plurality of light extraction features is a lowangle directing feature that redirects light at a first angle ofincidence to a second angle with an average total deviation less than110% of an angular difference between a first critical angle and asecond critical angle, the first critical angle defined by the firstrefractive index and the core refractive index and the second criticalangle defined by the second refractive index and the core refractiveindex.
 14. A display comprising: a. a reflective spatial light modulatorhaving a reflective surface; b. a first lightguide comprising a corelayer having opposing surfaces with a thickness not greater than 0.5millimeters therebetween, a lightguide region and a light emittingregion, the first lightguide defined by the opposing surfaces guidinglight by total internal reflection; c. an array of coupling lightguidescontinuous with the lightguide region, each coupling lightguide of thearray of coupling lightguides terminating in a bounding edge, and eachcoupling lightguide folded in a fold region such that the bounding edgesof the array of coupling lightguides are stacked; d. a light sourceemitting light into the stacked bounding edges, the light propagatingwithin the array of coupling lightguides to the lightguide region, withlight from each coupling lightguide combining and totally internallyreflecting within the lightguide region; e. a first cladding layerhaving a first side optically coupled to the core layer and an opposingsecond side; f. a plurality of light extraction features arranged withinthe light emitting region in a pattern that varies spatially in thelight emitting region, the plurality of light extraction featuresfrustrating the totally internally reflected light from the array ofcoupling lightguides propagating in the first lightguide between theopposing surfaces of the core layer such that light exits the core layerin the light emitting region into the first cladding layer; g. a lightredirecting optical element optically coupled to the second side of thefirst cladding layer, the light redirecting optical element comprising aplurality of light redirecting features directing a first portion of thefrustrated totally internally reflected light from the plurality oflight extraction features back through the first cladding layer and thecore layer to the reflective spatial light modulator; and h. a secondlightguide comprising the core layer, the second lightguide defined by asurface of the first lightguide opposite the light redirecting opticalelement and an area of a surface of the light redirecting opticalelement, such that a second portion of the frustrated totally internallyreflected light from the first lightguide propagates by total internalreflection within the second lightguide wherein the plurality of lightredirecting features occupies less than 50% of the surface of the lightredirecting optical element, the area of the surface of the lightredirecting element is defined between the plurality of lightredirecting features and reflects by total internal reflection a secondportion of the frustrated totally internally reflected light from theplurality of light extraction features back through the first claddinglayer and into the core layer where the second portion of the frustratedtotally internally reflected light totally internally reflects from thesurface of the first lightguide and is subsequently reflected by one ormore light redirecting features of the plurality of light redirectingfeatures toward the reflective spatial light modulator.
 15. The displayof claim 14 wherein the core layer has an average thickness in the lightemitting region, the light emitting region has a largest dimension in aplane of the light emitting region, and the largest dimension of thelight emitting region divided by the average thickness of the core layerin the light emitting region is greater than
 100. 16. The display ofclaim 14 further comprising a second cladding layer positioned betweenthe core layer and the reflective spatial light modulator, wherein thefirst cladding layer has a first refractive index, the second claddinglayer has a second refractive index less than the first refractiveindex, and the core layer has a core refractive index greater than thefirst refractive index and the second refractive index.
 17. The displayof claim 14 wherein each of the plurality of light extraction featuresis a low angle directing feature that redirects light at a first angleof incidence to a second angle with an average total deviation less than6 degrees.
 18. A display comprising: a. a reflective spatial lightmodulator having a reflective surface; b. a first lightguide comprisinga core layer having opposing surfaces with a thickness not greater than0.5 millimeters therebetween, a lightguide region and a light emittingregion, the first lightguide defined by the opposing surfaces guidinglight by total internal reflection; c. a first cladding layer having afirst side optically coupled to the core layer and an opposing secondside; d. an array of coupling lightguides continuous with the lightguideregion of the first lightguide, each coupling lightguide of the array ofcoupling lightguides terminating in a bounding edge, and each couplinglightguide folded in a fold region such that the bounding edges of thearray of coupling lightguides are stacked; e. a plurality of lightextraction features arranged within the light emitting region in apattern that varies spatially in the light emitting region, theplurality of light extraction features frustrating totally internallyreflected light propagating between the opposing surfaces of the corelayer such that light exits the core layer in the light emitting regioninto the first cladding layer; f. a light source positioned to emitlight into the stacked bounding edges, the light propagating within thearray of coupling lightguides to the lightguide region, with light fromeach coupling lightguide combining and totally internally reflectingwithin the lightguide region; g. a light redirecting optical elementoptically coupled to the second side of the first cladding layer, thelight redirecting optical element comprising a plurality of lightredirecting features directing a first portion of the frustrated totallyinternally reflected light from the plurality of light extractionfeatures toward the reflective spatial light modulator; and h. a secondlightguide comprising the core layer, the second lightguide defined by asurface of the first lightguide opposite the light redirecting opticalelement and an area of a surface of the light redirecting opticalelement between the plurality of light redirecting features, such that asecond portion of the frustrated totally internally reflected light fromthe first lightguide propagates by total internal reflection within thesecond lightguide, wherein the plurality of light redirecting featuresoccupies less than 50% of a surface of the light redirecting opticalelement.
 19. The display of claim 18 wherein the plurality of lightredirecting features occupies less than 30% of a surface of the lightredirecting optical element.
 20. The display of claim 18 wherein thecore layer is positioned between the light redirecting optical elementand the reflective spatial light modulator.
 21. The display of claim 18further comprising a second cladding layer positioned between the corelayer and the reflective spatial light modulator, wherein the firstcladding layer has a first refractive index, the second cladding layerhas a second refractive index less than the first refractive index, andthe core layer has a core refractive index greater than the firstrefractive index and the second refractive index.
 22. The display ofclaim 18 wherein each of the plurality of light extraction features is alow angle directing feature that redirects light at a first angle ofincidence to a second angle with an average total deviation less than 3degrees.
 23. The display of claim 18 wherein each of the plurality oflight extraction features is a low angle directing feature thatredirects light at a first angle of incidence to a second angle with anaverage total deviation less than an angular difference between a firstcritical angle and a second critical angle, the first critical angledefined by the first refractive index and the core refractive index andthe second critical angle defined by the second refractive index and thecore refractive index.
 24. The display of claim 18 wherein each of theplurality of light extraction features is a low angle directing featurethat redirects light at a first angle of incidence to a second anglewith an average total deviation less than 110% of an angular differencebetween a first critical angle and a second critical angle, the firstcritical angle defined by the first refractive index and the corerefractive index and the second critical angle defined by the secondrefractive index and the core refractive index.
 25. The display of claim18 wherein the core layer has an average thickness in the light emittingregion, the light emitting region has a largest dimension in a plane ofthe light emitting region orthogonal to a thickness direction of thecore layer, and the largest dimension of the light emitting regiondivided by the average thickness of the core layer in the light emittingregion is greater than 100.